# Let's design a sprinkler system for an actual house from start to finish.



## sprinklertech (Oct 24, 2010)

Let's design a sprinkler system for an actual house from start to finish.

Together we'll learn how easy this is to do and laugh at the homebuilders association who is trying to convince everyone sprinkler protection will add $15,000 to the price of the average home.

You know what CPVC pipe and fittings cost. Blazemaster might cost just a little more but it is nothing close to double. As far as sprinkler heads go I would expect them to cost $10 to $15 which would include the cost of the sprinkler head, escutcheon right, drop and adapter.

In the little house presented here I would guess all the sprinkler material could be purchased for $350 or less.

To make it easy on myself I use a form worksheet whenever I do calculations by hand. And yes, even though I have all sorts of nifty computer programs that do the calculations for me on real small jobs, especially standpipes in stairwells, I find it easier and faster just to do it by hand. 

If you would like to follow along, perhaps trying a layout of your own, you can find and print out a *copy of the worksheet here*.

I sketched out a single story three bedroom/one bathroom house that you can view *clicking here*.

It is a circulating system so it can be fed from domestic water without having to have a backflow preventor. The way I read it to be circulating all I would need to do is feed the toilet by dropping down in the bathroom wall at "A" so every time the toilet flushed the water circulates. There are no dead ends and this is part of the domestic plumbing.

Using this schematic I sprinkled the total hosue using only 8 sprinkler heads marked B through I.

You will notice the bathroom and closets do not have sprinklers.

From NFPA 13D "Standard for the Installation of Sprinkler Systems in One- and Two-Family Dwellings and Manufactured Homes" 2002 Edition we find:



> 8.6 Location of Sprinklers.
> 8.6.1 Sprinklers shall be installed in all areas except where omission is permitted by 8.6.2 through 8.6.6.
> 8.6.2 Sprinklers shall not be required in bathrooms of 55 ft2 (5.1 m2) and less.
> 8.6.3 Sprinklers shall not be required in clothes closets, linen closets, and pantries that meet all of the following conditions:
> ...


All of our closets are less than 24 sq ft and the least dimension on any of them is less than 3 feet. As you can see the bathroom is 6'-0" x 6'-7" for a total of 39.5 sq ft. far less than the 55 sq. ft..

The domestic water enters the pantry where I had domestic and fire separate. With domestic separated you can go do whatever it is you want to do, feed water heaters or whatever, as long as you use the end of the sprinkler line to supply the toilet so I don;t have a dead end.

For pipe from where it the domestic line splits (Pont "K" on my little sketch) the sprinkler would be Blazemaster. Blazemaster is listed and approved for domestic water and sprinkler use.

From Point "K to the street let's use type L copper. I know, most of you guys wouldn't do that preferring to use the black plastic pipe but I don't know what the inside diameter of that stuff is so I'll make it easy on myself using the expensive stuff.

We'll be running the pipe up in the attic right on top of the bottom chords of the roof joists so all attic pipe, with the exception to the short vertical drops to the individual sprinklers, will be run 8'-6" above finished floors.

The sprinklers will be fed with drops, size unknow for now, but they are short... less than 6" and it is my understanding these very short "dead ends" are allowed. I don't remember exactly where I read it but I remember seeing where dead ends up to 3'-0" were allowed. If you know and I am wrong let me know.

I've got all the pipe laid out but I don't have diameters... we don't know what that will be until we do our calculations. The dimensions on the pipe, such as the 13'-5" from sprinkler G to H are centerline dimensions.

The city watermain is at least 4" in diameter and the water department told us they maintain 60 psi on the main.

We are going to use.... drum roll please... the Viking FREEDOM® RESIDENTIAL PENDENT SPRINKLER VK468 (K4.9) *you can find by clicking here* as if you didn't see that one coming.

The last four things we will need is a *pencil*, access to the Engineering Toolbox with the *Online Hazens-Williams Calculator*, reference to *pipe ID's and equivalent fitting lengths that we can find here* and finally you will be needing a cheap scientific calculator. Doesn't have to be a $200 TI-85 or anything like that the one you need costs $9.99 at Target. Just make sure it has a square root and ^ function. I use the *Casio fx-300MS*. (The two line display comes in handy when you get older and can't remember what you did 10 seconds ago). 

Now you have everything you need to do a design job. 

Since you are just starting I'll let you in on something. Our problem child with this layout could be made up of the sprinkler in the kitchen (C) and sprinkler H in the living room but mostly likely I think it will be G and H in the living room. We're going to calculate both scenarios to make sure.

Because there isn't a lintel separating the kitchen, living dining area is considered one compartment and this compartment has three sprinkler heads in it. 

First we assign pipe sizes based on what we think the smallest pipe we use would work. I doubt it will work (honest, I haven't done it yet) but we're going to try 3/4" on everything to start but I think (I could be wrong) we're going to have to use at least some 1".

Take a look at what is here so far.

Taking a break, will be back.


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## PLUMBER_BILL (Oct 23, 2009)

*What 0 replies to this since 9:30 last evening ?*



sprinklertech said:


> Let's design a sprinkler system for an actual house from start to finish. <SNIP>
> 
> 
> I would say lets go for it. For a Person/Company wanting to do this.
> ...


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## sprinklertech (Oct 24, 2010)

Our very first step will be to prove a 3/4" feed is capable of adequately supplying Sprinkler "B" in the back bedroom.

While physically most remote this sprinkler will not be the "hydraulically most remote" sprinkler which is most likely reserrved for Sprinkler "G" and "H" in the living room. If 3/4" to the street works with G" and "H" you can make a safe bet it will work with "B" but some people have this idea most remote means farthest away which it doesn't. Just to placate these people I usually include a calc to the most remote head since, once you are used to doing it, takes but one or two minutes.

The farthest Sprinkler "B" is off any wall is 8'-0" so we will use the 16'-0"x16'-0" spacing requirement for the FREEDOM® RESIDENTIAL PENDENT SPRINKLER VK468 (K4.9) *here* and we see the minimum discharge is 13.0 gpm which requires 7.0 psi to operate.

In case you are wondering if you move that sprinkler so it is 8'-0 1/2" off the farthest wall the discharge requirement will jump to 17.0 gpm which requires 12.0 psi and sometimes a jump like this can hurt you. It is important to remember things change in the field. Perhaps they have to move the sprinkler because a floor joist is in the way or maybe the HVAC guy beat them on the job taking the joist space I indicated. To get around this I tell my workman they have certain peramiters and most likely I would tell them they can change to anywhere they want in the room as long as they do not exceed 8'-0" from the farthest wall. Sometimes this will change the hydraulics in the pipe but in a case like this I can not see it changing so much it wouldn't work or I couldn't recalc it if I had to. Just remember in this case 8'-0" off the farthest wall, whatever wall it is, is important.

Reference points, for example sprinklers marked "B", "C", "D, or fittings such as tees, need only be marked under the following conditions:

1. If water is added such as a flowing sprinkler head. 

2. Anytime their is a change in pipe type (C-Value) or diameter. In our first exercise (flowing water from Sprinkler "B" all the way to the street connection) we are going to need to have only two reference points which greatly reduces our calculation work in this case to a two step process.

On our first example our first reference point will be the actual sprinkler head and the second will be at point "K" where the domestic water splits off. The reason for Point "K" is we are changing pipe diameters.. we already said we are using Blazemaster for the sprinkler and copper from the street. Even though this might be all 3/4" or 1" or even 1 1/4" the actual internal diameter of the pipe changes at Point "K" where we transition from Tye L copper to Blazemaster.

*I think you will be amazed at how easy the process really is once you understand "the system" of doing things. I have said it before but I am convinced any of you reading this can do this if only you give a couple days, maybe three at most, in diligent study by actually doing and following the examples. At day three a light bulb will go off and you'll say to yourself "that's really easy" because it is. *

3. We need a reference point anywhere we "split" a flow such as a loop or grid connection. Loops can greatly help in cutting down pipe sizes and I I do plan to discuss how to calculate loops they are a little more difficult (not greatly once you see how it is done) and maybe I will get into loops next week. But for now lets stick with straight single directional feed systems leaving the real fun for next week.:thumbsup:

First thing we will do is add up the total linear footage of 3/4" pipe from Sprinkler "B" to Reference Point "K" which is where the domestic splits off. I count 0'-6"+19'-9"+1'-7"+5'-0"+9'-1"..... all the way to the last pipe length of 7'-6" for a total of 133'-1". Did everyone get that?

If you are 0'-6" off in your count you forgot to include the 9'-6" in the drop from the tee at point "B" to the actual sprinkler head.

We convert 133'-1" to decimal feet which is 133.08'.

Try to be as accurate as you can be but we all realize this job will not go in perfectly. The guys doing the installation are going to pick up an inch and drop an inch here and there so you really don't have to sweat hundredths of an inch and if you would want to round up to the nearest 3" you'd be just fine.

It isn't Swiss watches.

Now for the fittings.. how many tees with flow turning 90 degrees do we have? I count one (1) and that is the tee at the drop for Sprinkler "B".

How many elbows do we have? I count a total of eight (8). You count the same thing?

How many tees having flows straight through do we have? I count seven (7). We do not count the tee at Sprinkler B because that tee was already counted as the tee that turns water 90 degrees. Sprinkler B tee is not a flow through tee. We also did not count the tee where the domestic splits off because that is on the copper side... we will pick that up in our second step.

How many couplings did you count? I count two (2). Yeah, I am being punk ass here but we would have two because I know Blazemaster only comes in 15'-0" lengths... we will need at least two couplings on the two pipes longer than 15'-0". 

Time to take a look at Step #1 of our calculations (we're halfway done)!










What we see here is we need to have a pressure of 29.1 psi at Point "K" (where the domestic line splits as shown in the cross section) with a total flow of 13.0 gpm to adequately supply Sprinkler "B".

The Pe is the pressure we need to have to compensate for the change of elevation. A water column weighs 0.433 psi per foot and when we dropped from the sprinkler head (the discharge point) that is located 8'-0" AFF to a point 1'-0" AFF (total drop in elevation of 7'-0") we need to add 7.0*0.433=3.0 psi to "lift" the weight of the water.

Under Pipe Fittings and Divices I used a captial "T" to note a tee with 90 deg turn. I used a small "t" to note the total equivalent pipe length through 7 't''s which is 7'-0". The elbows kind of beat us to death with 8 elbows (8E on hydraulic calc page) equal to 56' of 3/4" pipe. Then we added the two couplings "C" and ended up with a total fitting equivalent pipe length of 68.0 feet. Add this 68.0 feet to the actual pipe length of 133.1 feet and we got a total equivalent pipe and fitting length of 201.1 feet.

Our online Hazen Williams calculator indicates that with 13.0 gpm flowing through a pipe having a diameter of 0.874" and a C Value of 150 we can expect a head loss of 0.095 psi per linear foot. 

0.095*201.1=19.1 which is what we used. Total friction loss from pipe and fittings was 19.1 psi.

Now one more step and that is calculating the loss to the city water main.

Note: If you are confused please do not hesitate to PM me. Trust me, you would not be the first a little confused just getting into this so don't feel bad.


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## sprinklertech (Oct 24, 2010)

Our next step is to carry the water from the house through the underground to the connection in the street.

You should have something that looks like this:










Remember step #2 involves Type L copper so I could use the equivalent fitting lengths for copper which are slightly smaller.

However the internal diameter for copper tube is smaller.

In any event what this tells us is we need to have 35.3 psi at the street in order to adequately feet a single sprinkler operation with 13.0 gpm inside this house.

But we have ONE MORE STEP.

We have a water meter and have to add in that loss to the 35.3 psi.

NFPA 13D has a table for typical pressure loss through meters.










In my opinion they could work on this a bit.

Assuming we have a 5/8" meter there is a 9 psi loss flowing 18 gpm but we're only flowing 13.0 so what to do?

We could avoid all argument from inspectors and just call it 9.0 psi. By adding 9.0 psi to the 35.3 psi our system (so far) requires only 13.0 gpm at 44.3 psi which is well below the 60.0 psi the city reported they had. Doing this is fine and I've yet to hear where a review official hasn't accepted something like this.

Let's talk about "safety factor" for a moment. NFPA standards allow you to take your calculations right up to 60 psi but in my opinion I like leaving a 10 psi "safety factor" between what my requirement and actual psi available is. It's just good practice and in some locations a safety factor is required. The most I have heard of is 10.0 psi (Georgia) while many states require a percentage usually 5 to 10%.

Some states don't require any.

I like to leave 10 psi because if something changes I do not want to start ripping walls out to fix it. Let's be real, is the price difference between 100' of 3/4" and 1" really that great to take a risk over? What are we looking at, $40 on the high side?

Back to meters for a second. If you know exactly the kind of water meter that will be used you can always use the manufacturers numbers. This is allowable and it is normally always less.

For example let's take a *5/8" Neptune T-10 meter* flowing 13.0 gpm.

According to the *product sheet here* (bottom of page 2) we would have a 3.5 psi pressure loss flowing 13.0 gpm. That's a lot better than the 9.0 psi the NFPA has us use and it is totally acceptable to use it.

It is important to note the NFPA table is what you are supposed to know if you don't know exactly the make and model of meter that will be used. If you don't know what it will be you are safe using the 9.0 psi but if you know, and you have to be dead on correct, you can use the manufacturers literature.

So yes, you could say our single head system for the bedrooms requires 13.0 gpm @ 38.9 psi.

About our calculations. There are two ways to do them.. the "easy simplified way" is to use the charts and tables in NFPA 13D or you can use the methods outlined in NFPA #13.

The method demonstrated to you here is in accordance with NFPA #13 (I honestly don't believe it is any harder to do) and it offers the following advantages.

From NFPA #13D:



> 8.4.5 Smaller pipe sizes than those determined by 8.4.4 shall be permitted where justified by calculations for systems connected to city water mains of at least 4 in. (102 mm) in diameter.
> 8.4.6 To size piping for systems with an elevated tank, pump, or pump–tank combination, the pressure at the water supply outlet shall be determined and the steps in 8.4.4(3), (4), (7), (8), (9), (10), and (11) shall be followed.
> 8.4.7 Hydraulic calculation procedures in accordance with NFPA 13, Standard for the Installation of Sprinkler Systems, shall be used for grid-type systems.
> 8.4.8 *Hydraulic calculation procedures in accordance with NFPA 13, Standard for the Installation of Sprinkler Systems, shall be used for looped-type systems.*
> 8.4.9 *Hydraulic calculation procedures in accordance with NFPA 13, Standard for the Installation of Sprinkler Systems, shall be used for systems connected to city water mains of less than 4 in. (100 mm) in diameter.*


As I said before loops are not that hard to do and we are going to be doing them in a week or so. Using loops can GREATLY cut down on overall pipe sizes. 

Well I am tired, I should be back tomorrow evening.


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## PLUMBER_BILL (Oct 23, 2009)

Genltlemen, On this topic there has been 115 views and 3 replies.
the law takes effect that on January 1, 2011 all single family homes built will have sprinklers in them. Now at my age I probably will not ever do a new home again. But do I have to know fire systems? How to calculate it? I say the answer is yes. Suppose I as a plumbing contractor in the future have to change a piece of pipe. Lets say it's 1" and the homeowner wants to have it relocated because of a remodeling job. I figure hell I can do this with 3/4" and there will be no problem. Well if the house had a combo fire system. per sprinklertech I by doing that would change all the calulations and maybe the fire suppression would not work as designed. The house is destroyed and somebody died. Who do you think is getting sued? 

Comments ... please!


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## sprinklertech (Oct 24, 2010)

PLUMBER_BILL said:


> Genltlemen, On this topic there has been 115 views and 3 replies.
> the law takes effect that on January 1, 2011 all single family homes built will have sprinklers in them. Now at my age I probably will not ever do a new home again. But do I have to know fire systems? How to calculate it? I say the answer is yes. Suppose I as a plumbing contractor in the future have to change a piece of pipe. Lets say it's 1" and the homeowner wants to have it relocated because of a remodeling job. I figure hell I can do this with 3/4" and there will be no problem. Well if the house had a combo fire system. per sprinklertech I by doing that would change all the calulations and maybe the fire suppression would not work as designed. The house is destroyed and somebody died. Who do you think is getting sued?
> 
> Comments ... please!


Certainly this will be part of the professional plumbers work. These combination systems were designed for plumbers to do the work.

Right now new home construction is down but it will come back. Maybe in two, three or four years but the economy always gets better and when it does we will see new houses being built. In many areas of the country these new houses will have fire sprinkler systems.

The calculations are not that hard to do (just really different from what you are used to doing) and in many areas of the country the local code officials will accept the design work of a licensed plumber. In other areas of the country the design work will have to be done by a *NICET* certified engineering technician holding Level II, III or IV in *Automatic Sprinkler System Layout*. I know the state of Washington requires NICET II while other states, such as Alabama, nothing is required but a plumbers license as far as I am aware. In Pennsylvania it is going to depend where the work is done. Some areas will accept a plumbers license and others will end up requiring NICET.

Getting someone to prepare the drawings and calculations is easy... there's a couple thousand of us NICET guys out there that will be happy to prepare drawings and calculations for a couple hundred bucks and you can find these people by google NICET Freelance.

By being able to do the work yourself you will keep the costs down. I am not soliciting business (I am to busy) but if you wanted me to draw one up I would happily do it for $150 to $250 cash money seeing as how I could do this at home in my spare time inside of two to three hours tops but only if you provide me with all the information I need.

The best way for you to know what I need is for you to know how to do it yourself which is the reason I am doing this little project. If you don't have any idea and it is up to be to discover how far the city water main is from the house, what material is used, meter size and model, city water pressure and a half assed floor plan I could do all that but it will cost you.

Floor plan..... I could care less about a floor plan what I want to see is a ceiling plan. I don't need to know where the carpet begins and ends, I don't need to know about the kitchen linoleum but I do need to know about lights, lentils and HVAC diffusers. I also need to know other things like what way the joists run (helps you in installation) and *actual room dimensions*. There is a difference between 16'-0" and 16'-1" so be as exact as you can be.

If you know and understand how one lays out you will know the information I need so you can get it to me. You get me all the right information so I can push this job out in 2 to 4 hours and we'll negotiate on a price lower than anywhere else.

If you don't know how to do it how do you know what I need?

Also, if a plumber called me saying "use Viking VK435 pendents wherever there are two or more heads in a compartment and use the Viking VK 468 sprinklers wherever you can maintain an 18'x18' spacing to keep the size of the service and meter at a minimum" would I ever be impressed! I really would be. Now I know I have someone I can work with and be comfortable with... he knows what he wants.


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## luv2plumb (Apr 30, 2010)

That was just like sitting through class all over again. I have already recieved my TX Master Endorsement for resi. fire sprinklers. As far as I know TX requires the plans to be designed by an engineer. Keep on getting the word out there. Just like the quote from Field of Dreams "If you build it; he will come"


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## sprinklertech (Oct 24, 2010)

luv2plumb said:


> That was just like sitting through class all over again. I have already recieved my TX Master Endorsement for resi. fire sprinklers. As far as I know TX requires the plans to be designed by an engineer. Keep on getting the word out there. Just like the quote from Field of Dreams "If you build it; he will come"


Latest *requirements for Texas*.


> (B) RME-Dwelling:
> (i) proof of current registration in Texas as a professional engineer; or
> (ii) a copy of the notification letter confirming at least a 70% grade on the test covering dwelling fire protection sprinkler systems, administered by the State Fire Marshal's Office or an outsource testing service, and one of the following:
> (I) proof of license as an "RME-General"; or
> ...


For non-dwelling fire sprinklers drawings must be prepared by a licensed Texas professional engineer or the hold of a NICET III certificate. The engineer or NICET III certificate holder is the RME and must be employed by the sprinkler company full time in order for the company to maintain a license.

Now it appears they have a separate license for sprinklers in one and two family dwellings and it has some changes.

Unless I am reading the statute wrong the RME for the dwelling license does not have to work full time for the plumbing company and he doesn't have to be NICET III he can be NICET II.

This seems to be reasonable and what you need to do is find a Level II certificate holder that will work on a part time basis. Strange, he has to work for another company to be able to work part time for the dwelling sprinkler company. You know why that is?

Checking the NICET registry Texas has 67 Level II's, 194 Level III's and 81 Level IV'S for a total of 342 people in the state that could hold a dwelling RME.

States are going to be in a delicate balancing act when it comes to licensing and regulation. They can't make it so stringent to the point where nobody can do the work (I can tell you right now fire sprinkler companies will not be tying into your domestic because we are not licensed for that) but they got to keep enough regulation in place to insure the work is done right.

It is going to be interesting how these laws develop.


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## sprinklertech (Oct 24, 2010)

Back to calculating the flow of one sprinkler head, which we finished, but the final calculation worksheet should look like this










Now we need to calculate sprinkler heads G and H. 

Perhaps an argument can be made heads C and H are the most hydraulically most demanding but they aren't. If you want to double check feel free to do so but remember the required discharge from head C is 13.0 gpm (smaller area) while C and H will both require 20.0 gpm.

I can also tell with certainty this will fail miserably on a 3/4" line. I think we will need a 1" line with a 1" meter but we will see.

First we will attempt the impossible by trying to prove it can be done with 3/4" but before we do I can tell you with reasonable certainty there is a way to properly lay out a system where 3/4" feed and 5/8" meter will work.

But first let's press forward with a miserable attempt to show we can do it as currently laid out.


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## sprinklertech (Oct 24, 2010)

We are calculating sprinklers G and H and our first step is relatively easy.

Your worksheet will look like this at the completion of step #1.










We are flowing sprinkler G to Reference Point H with a flow of 20.0 gpm.

20.0 gpm is required because our spacing (19'-0") requires the VK468 sprinkler to discharge 20.0 gpm which requires 16.7 psi.

Our total pipe length is 13'-11" (converting to decimal 13.9 is close enough) and we have two fittings. 

Wait! The drawing shows the pipe distance from G to H to be 13'-5" so how did I come up with 13'-11? Remember, we have the 0'-6" drop from the tee to the actual sprinkler head and to be accurate we have to incorporate this length into our calculations.

You will also notice we actually gained 0.20 psi in the elevation. Anytime you increase elevation (we increased 0'-6" between the actual sprinkler G and the fitting at the top of sprinkler H) you subtract the weight of the column of water. When you move from a higher to lower elevation you add the column of water.

What step #1 tells us is we must have 20.0 gpm at the tee of reference point H with 20.3 psi in order for the sprinkler at G to discharge 20.0 gpm at 16.7 psi.

For fittings we have two. We have the Tee with a 90 degree change in direction at reference point G and we have a run through T at reference point H. The T with a 90 degree turn has 3' of equivalent length while the run through T has 1'. The total equivalent length for pipe and fittings is 17.9 feet.

Now we have to add the 20.0 gpm at sprinkler H but this does not involve simple addition of 20.0 gpm for a total of 40.0.

Think of it this way. If we have to have 20.3 psi at the tee feeding sprinkler H to be able to have sprinkler G discharge 20.0 gpm doesn't it stand to reason that sprinkler H will actually discharge more water because it is supplied by a higher pressure?

This is the same concept of having two lawn sprinklers in series fed with a garden hose. If you have 50' of hose and you put on a garden hose tee feeding a lawn sprinkler then have another 50' of hose feeding an identical sprinkler at the end doesn't the sprinkler closer to the water supply (hose Bib) discharge more water? Of course it does, we've all seen this phenomena with our own eyes..

It is the same thing with fire sprinklers.

Step #2 will involve calculating the friction loss from the sprinkler at point H to the tee or reference point at point H. We will assume 20.0 psi and calculate our loss through 0'-6" of 3/4" Blazemaster pipe so we can determine how much pressure we need at tee H to supply sprinkler H.

The second step will look like this.











The required pressure at the Tee that represents point H requires 20.3 psi to adequately supply sprinkler G but to feed sprinkler H right below the tee all we need is 17.2 psi.

Obviously we have to have 20.3 psi for the system to work so the question is if we had 20.3 psi at H how much water would sprinkler right below discharge? Obviously it is going to be more (the more pressure the more water comes out) but how much more?

We can determine this by finding the discharge coefficient (or K-Factor if you want to use a less imposing term) of the lower pressure by the formula

K=q/p^.5 or k=20.0/17.2^.5 or *k=4.82*

The discharge coefficient for sprinkler H at the tee is 4.82.

Now we can determine how much water the sprinkler will discharge at 20.3 psi by the formula q=k*p^.5

q=4.82*20.3^.5 or q=4.82*4.50

*q=21.7 gpm.*

What we will have is a total of 41.7 gpm with 21.7 gpm discharging from sprinkler H and 20.0 gpm from sprinkler G. Like the garden hose with two lawn sprinklers in series.

If it is a little bit fuzzy and confusing (I am sure it is to 99% of you) you are not alone. Most are trying to figure out WTH sprinklertech is talking about but it is something you have to work on. It's going to take a few days of study and having trained a number of people over the years I can tell you *nobody "gets it" in a day* and nobody here is stupid.

It helps if you think about it.. think of what you have seen... the best analogy I can think of is the two lawn sprinklers... why are they behave like that?

We continue on to reference point K with our total flow of 41.7 gpm through 3/4" Blazemaster and immediately see we have problems.

We need to have 67.5 psi at reference point K to make this work and seeing as how the city doesn't have that much, not to mention we haven't calculated the head loss from the house to the city connection, there is no way this will work. Right now you could run 8" underground to the stree and it will not work.









*What if we used 1" from the reference point H to K instead of 3/4"? Larger pipe=less friction loss when flowing equal amounts of water so we might as well give that a try.

*The bad part about 1" is many cities will charge more money for the capacity charge and 1" meters do cost more.


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## sprinklertech (Oct 24, 2010)

Here's our results using 1" instead of 3/4".










With 60 psi available we could lose 21.0 psi from K to the street and through the meter but we will not be able to use 3/4". At a minimum we will need a 1" feed and 1" meter.

1" doesn't do it either.










We have 60.0 psi available at the street and calculations show we need 62.9 psi.

The next step might be to go to a 1 1/4" meter but that nearly always causes problems with tapping fees, permits and the minimum monthly water charge based on "capacity charges" that some cities have.

But there is a way to make this work. What if we replaced the 3/4" pipe used 1" pipe from sprinkler G to H?

I am pretty sure (positive really) that this would do the trick so we will change the 3/4" drops from the tees to sprinkler heads to 1" and change the piece of pipe from G to H to 1". In real terms this might be a $10.00 fix but I doubt it would cost that much.

Is everyone following me so far?


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## sprinklertech (Oct 24, 2010)

And finally it works!










*But there is a big but of caution.*

This works, it meets the standards and better than 90% of the jurisdictions in the country would accept it but I wouldn't certify the drawings and calculations.

Our system requires 58.9 psi to operate correctly and since we have 60 psi it passes. 

This is just my opinion but I always like to see a 10 psi "safety factor" in all of my designs. What happens if the installing plumber has to use a few more elbows in the kitchen pantry? What happens if it turns out the city water main is really 10' or even 20' farther out in the street than the city water department told you it was? Think about it, has the city ever told you something that ended up not to be true when you started digging? Right......

What I would want to do is design a system that would not require more than 50 psi to operate and if I can get that down to 45 psi I would sleep even better at night.

I am also concerned about the 1" meter, is there some way we can design this thing so the 3/4" line and 3/4" (maybe even a 5/8" meter) will work?

*You betcha there is.

What if we added some extra sprinklers like this?










*Using *Viking VK468 sprinklers* in the compartments where only one sprinkler is required while using the *Viking VK435 sprinkler* in compartments where two or more sprinklers are required.
The advantage is the minimum required water discharge for the VK468 sprinkler is 13.0 gpm but the minimum discharge for the VK435 sprinkler is just 9.0 gpm if spaced 12'x12' and 10.0 gpm if spaced up to 14'x14'.

If we spaced these sprinklers to a maximum of 12'x12' the water demand for a two sprinkler compartment would most likely be only slightly more than 18.0 gpm. This is less than HALF the water in this home using VK468 sprinklers throughout.*

Another interesting thing is I can tell you with this layout our hydraulically most remote area in this case will be the hallway sprinklers B and C. It will not be the living room area but the hallway which has two sprinklers.

What we are looking for is the hydraulically most demanding area and these areas don't always fit our ideas on what the "most remote" area should be. Depending on the hazard, coverage and specific sprinkler used the hydraulically most remote area can be literally anywhere. An experienced design technician can generally look and tell where the hydraulically most remote area will be but sometimes even your most experienced design technician might even have to do two, three or even four different sets of calculations to "prove" the hydraulically most remote area is the hydraulically most remote area. For residential this isn't hard or time consuming. Given experience, which you can get only by practice and working at it, a typical set of calculations should take you 5 to 15 minutes and, in residential, most systems will take two, maybe three, sets of calculations. You can figure something out like this over the mornings first cup of coffee but you need to practice at it.

*


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## PlumberJake (Nov 15, 2010)

*Thanks*

I have been wondering about residential sprinkler systems. Your knowledge and teaching ability is much appreciated. :notworthy:

I look forward to the upcoming posts.

Jake


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## sprinklertech (Oct 24, 2010)

We've hit some pretty heavy stuff over the past week and in hopes of enjoying a little break I thought we would clarify the hydraulic calculation procedures in NFPA #13.

I some ways sprinkler people have it easier than plumbers. When you think about it we do.

Fir example I have often heard plumbers discuss interpretations by the local authority having jurisdiction. Seems to happen often in your world but to be honest it seldom happens in ours.



> 14.4 Hydraulic Calculation Procedures.
> 14.4.1* General.
> 14.4.1.1 *A calculated system for a building, or a calculated addition to a system in an existing sprinklered building, shall supersede the rules in this standard governing pipe schedules, except that all systems shall continue to be limited by area.*
> 14.4.1.2 Pipe sizes shall be no less than 1 in. (25.4 mm) nominal for ferrous piping and ¾ in. (19 mm) nominal for copper tubing or nonmetallic piping listed for fire sprinkler service.
> ...


Basically that tells us we can pretty much do anything we want to do as long as we can prove it will work. 

For example what if we ran all the interior pipe 1 1/4" diameter, tan 1 1/4" to the 3/4" copper entrance and used the 3/4" existing copper for our feed. Would a piping scheme such as this be be allowed by the applicable sprinkler standards?

I am sure you can point to many areas of plumbing codes where something like this would not be allowed (I am just thinking this because I really don't know all that much about plumbing but I'm just basing my guess on some of the things I have heard) but it is perfectly permissible for sprinklers. Remember, when it comes to sprinklers the *ONLY* thing that matters is:



> *The size of pipe, number of sprinklers per branch line, and number of branch lines per cross main shall otherwise be limited only by the available water supply.*


We got it easy, don't we?


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## sprinklertech (Oct 24, 2010)

In hopes of clearing up a little confusion it is important to remember the way we do calculations is completely opposite of what intuitive reasoning might lead one to believe. Intuitive reasoning might have one think the correct way would be to start at the street and work towards the hydraulically most remote sprinkler when the reality is we start with our calculations at the most hydraulically remote (most demanding is a better term) and work our way towards the street.










When we start our calculations the first step will be to calculate the friction loss from the sprinkler B to the tee located on top of sprinkler C a total linear distance of 11'-6".

Our second step will be to calculate the friction loss from sprinkler C up the 3/4" drop (sorry but I even think backwards.... years of habit) to the reference point C which is the tee on top of sprinkler C. 

Actually at point C there are two reference points. One designates the actual sprinkler head at the ceiling elevation and the other designates the tee which is 0'-6" higher than the sprinkler.

As always if you have any questions feel free to ask or PM me if maybe you are embarrassed thinking you are the only one that "doesn't get it". I can promise if you are one of those following along, trying to do it, you are not alone in "not getting it" or, as we all have had when we started, feeling sometimes a little lost so I don't want you feeling bad. If you work at it you will get it.


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## sprinklertech (Oct 24, 2010)

So we tried running the entire system in 3/4" and to my surprise (I really thought it would work) we didn't make it.










By running 3/4" throughout, with a 3/4" water meter, we require 67.5 psi and since it is higher than the 60 psi available no cigar for us on this one.

But what if we simply change the 3/4" from reference point C to reference point G to 1" while leaving the underground at 3/4" along with a 3/4" meter?

Remember, pipe sizes are not governed by any sort of schedules or pre-set sizes. 

I tried it and it works nicely!










In fact we have an 18.7 psi "safety factor" and in this system we could even make due with a 5/8" meter. 

But there are other ways you can make 3/4" work and that is by using "loops".


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## sprinklertech (Oct 24, 2010)

Before we go further I want to offer some clarification on calculations and the way I do things. 

I have learned to be cautious and you can see this is my desire to maintain a 10 to 15 psi "safety factor" in my calculations in case something doesn't go in exactly as I figured it would. I won't cut something so close to the point where an installer uses four more elbows than I figured (perhaps going around duct or some other obstruction) the system won't work as intended. 

Shaving material to save $20 in material simply is not worth taking any risks. I always error on the side of caution and you should too.

Up to this point you will notice I have used equivalent fitting losses for flow through tees (this is where the flow is straight though the run of a tee) and I am pretty sure we don't have to do that.

NFPA #13D offers an simplified method for calculations but what I have covered here is not the simplified method but the full NFPA 13 method. I don't care for the simplified method because in my mind it really isn't all that simplified and it takes to many tools out of our toolbox such as using loops which I am going into next.

The friction loss through runs in tees is covered in NFPA #13D but the complete opposite is called for when calculating a system per NPFA #13 per section 13.3.3.5:



> 14.4.4.5 Friction Loss. Pipe friction loss shall be calculated in accordance with the Hazen-Williams formula with C values from Table 14.4.4.5, as follows:
> 
> snip
> 
> ...


So if we use the simplified method in 13D we are supposed to include the equivalent lengths of flow through tees but if we use the calculation method of 13 it tells is the exact opposite that we should "*not include fitting loss for straight-through flow in a tee or cross."

*Ok, I've never used the simplified method but *when using CPVC* I have always used the equivalent length of a flow through tee *even though NFPA #13 tells me not to. *I can assure it including the equivalent length through a run never adversely impacts the calculations the worst thing it will do is add to your safety factor which is never a bad thing to begin with. Straight runs through tees are not included in the table of equivalent fitting lengths in NFPA #13 but you sure find them in the CPVC manufacturers tables so to error on the side of caution I use them even though I know I have plenty of standing to argue I don't "have to".

In pipe lengths I want you to know there is nothing wrong with rounding pipe lengths up to the nearest whole foot either. So far we haven't done it here but if your pipe between two sprinklers is 11'-7" there's nothing wrong with just calling it 12'-0" and go on. The worst that can happen is you might be four tenths of a pound off (to the good may I add) and let's be honest; cities don't measure pressure in city water systems by the tenth of a pound. 

Let me be clear, nothing wrong with rounding a length up but you *never *round it down.

But one thing I do follow, whether it is CPVC or steel, is I never include the fitting directly connected to the sprinkler. If the sprinkler is directly connected to a tee I do not nclude the equivalent fitting length of that tee into my calculations.



> (9) *Friction loss shall be excluded for the fitting directly connected to a sprinkler.*


So we try to be as accurate as we can but we're not building Swiss watches.


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## sprinklertech (Oct 24, 2010)

The easiest and most reliable way for us to decrease our pipe size is to incorporate loops into our system.

Consider the following.










One way to calculate the split and flow is to use the Hardy-Cross method which *you can explained in this tutorial here*.

Once you master that we're ready to move on!

*Ok, sorry.... I am messing with your mind.... nobody around these parts is going to master that mess **including yours truly. I have a confession to make, I am not that smart.*

Hope I didn't scare anyone off.

To obtain certification I had to pass advanced hydraulics which included calculating a simple grid (as if there is such a thing) and to prepare I hired my daughters high school algebra teacher to tutor me a three evenings a week for a few hours a night over a period of a couple months. The tutoring was almost entirely on the Hardy Cross method and I only needed to know how to do it to pass the test. Once I passed the test I figured I could forget about how to do it and I did. 20 years ago with hard work I could solve a grid using Hardy Cross but I couldn't do it today if my life depended on it.

Today we have computers and really neat, nifty computer programs that solve the problem for me in seconds instead of days. 

But we not going to do a complex grid we're going to work on simple loops and there's an easy way to solve those we'll use "brute force" instead of the more elegant Hardy Cross method.

We're going to use Iteration. _Iteration_ means the act of repeating a process usually with the aim of approaching a desired goal or target or result.

So what we are going to do is knowing we have 20.0 gpm flowing in, knowing it has to split and total 20.0 gpm at the head again why not use iteration to find how much water flows through each side to produce equal total friction loss?

We could start out with 10.5 gpm on side A with 9.5 on side B. Then maybe 11.0 on side A and 9.0 on side B. Just go back and forth, might take half a dozen times, until we solve it. 

Even if you are not doing sprinklers this sort of thing helps in your understanding how water flows through pipes. Certainly can't hurt.

Be back in a bit with some answers.


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## 6th Density (Nov 29, 2010)

Thanks for all the info. It will take me a good weekend to try and absorb it all. I've only ran one residential sprinkler system in my career. It was for the owner of the company. It was the first time toying with with the orange cpvc (Blazemaster?) Our project manager gave us some engineered prints on the layout and let us loose...
It was kinda fun doing something new. 

I've noticed here in Panama City that the local Fire Department has found a new way to create revenue. They are going around to commercial businesses and assessing their risk for each building's roofs burn factor. Hitler would be proud of them! So now they go around and slap each business a 50 dollar fee to inspect their roof construction. If a business has their building inspected (MEANING ALL) then they get a cute little sticker (ABOUT 8" IN DIAMETER) they get to put on their front door stating the code of potential roof fire hazard they are in. 

And now you are bringing up the fact that for your area, all houses to be built after jan 1st. must have fire sprinklers.
How much longer before the fire department goes after residential!!.

Thank god I don't live in a city!!!:furious:


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## sprinklertech (Oct 24, 2010)

Let's try some iteration to solve the loop.


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## Mpls Jay (Jan 1, 2011)

Uponor/Wirsbo is into the fire protection game also.


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## bml (Feb 8, 2011)

A very informative thread!


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## Tommy plumber (Feb 19, 2010)

I have a question. It might seem elementary for a licensed fire sprinkler contractor, but remember I am a plumber. I have no formal training in fire sprinklers.

My question is, are there any parts of a residential or commercial bldg that gets extra sprinkler head placement, or are all areas equal and therefore sprinkler head spacing equal in all parts of a bldg? (if you've already answered this, I'm sorry). You stated you didn't need to know where the carpet ends, or if kitchen floor was linoleum, but I need to still ask.


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## Tommy plumber (Feb 19, 2010)

sprinklertech said:


> We've hit some pretty heavy stuff over the past week and in hopes of enjoying a little break I thought we would clarify the hydraulic calculation procedures in NFPA #13.
> 
> I some ways sprinkler people have it easier than plumbers. When you think about it we do.
> 
> ...


 


Not only that, but fire sprinkler contractors only have to get water into a bldg, not out. We plumbers have to get the water into a bldg and then make provision to get it back out.


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## sprinklertech (Oct 24, 2010)

Tommy plumber said:


> My question is, are there any parts of a residential or commercial bldg that gets extra sprinkler head placement, or are all areas equal and therefore sprinkler head spacing equal in all parts of a bldg? (if you've already answered this, I'm sorry). You stated you didn't need to know where the carpet ends, or if kitchen floor was linoleum, but I need to still ask.


We are limiting the discussion to NFPA 13D "*Standard for the Installation of Sprinkler Systems in One- and Two-Family Dwellings and Manufactured Homes*" - 2002 Edition because that is what I still use in my jurisdiction.

If you are asking if a storage room gets extra sprinklers, because it is combustible storage as compared to a bedroom with little storage for example, the answer is no.

The combustibility of the room doesn't make for a bit of difference. Whether it is concrete or wood, press board or drywall the construction type doesn't make any difference in the location or placement of the residential sprinkler head.

But what may cause an extra sprinkler to be required would be an obstruction such as a beam.

As far as non-structural obstructions while I do try to avoid them they are addressed in NFPA 13 "Standard for the Installation of Sprinkler Systems" 2002 Edition (yeah, I know NFPA 13 isn't the 13D but in some areas it does apply):










The key here is at the bottom Section 8.6.5.3.2.4. Obstruction clearance only applies to structural members in light and ordinary hazard occupancies and any residential occupancy is defined as light hazard.

This isn't going to make any sense (it doesn't to me but I didn't write the standard) but for obstruction clearance if I have a light fixture that hangs down 12" I can ignore it but if a beam hangs down 8" I have to take it into account when placing sprinklers. Go figure, huh?

That all said when laying out a system I do try to avoid obstructions with lights not because I am required to (Section 8.6.5.3.2.4 says I do not have to) but because I feel it is the better thing to do. Above all I want the system I install to perform well if called upon.

I mentioned residential occupancies were defined as "Light Hazard" which comes from the appendix of NFPA #13 section A.5.2:


> *A.5.2 Light hazard occupancies include occupancies having uses and conditions similar to the following:*
> Churches
> Clubs
> Eaves and overhangs, if of combustible construction with no combustibles beneath
> ...


Did I answer the question well enough?


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## Tommy plumber (Feb 19, 2010)

Yes sir, thank you very much...:thumbsup:


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## Paddy (Sep 2, 2011)

Here is the bottom line about residential sprinkler design. Plumbers have access to plumbing suppliers who will design the sprinkler systems for them. You send the supplier a floor plan and information about the water supply, and a qualified sprinkler system designer will send you the required drawings. 

Not all plumbing suppliers are alike. The best designs will include all of the plumbing fixtures in the same design, one that maximizes the hydraulic efficiency of plumbing fixtures and sprinklers. The result is a water distribution system that is more effective for plumbing and sprinklers - while costing less than separate systems.


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## Paddy (Sep 2, 2011)

A followup on my last post. The Hydratec software that Uponor and other plumbing suppliers use to design residential system loops and grids is now available to independent designers. It is called HYDRACAD-R, and Hydratec sells two versions. Designers who already have AUTOCAD can get it for $2K. If you don't have AUTOCAD, Hydratec has an OEM version for $3K. If you are interested or just curious, I recommend that you visit the Hydratec web site and view their HYDRACAD-R demonstration. 

One cool thing I found was that the software includes an up-to-date library of sprinklers listed for residential use. Once the designer selects the desired sprinkler, say a Reliable F1 pendent, the program enters all of the needed data (e. g., K factor, minimum required pressure and volume) into the calculations. 

This news is heartening to me for several reasons. For one, the cost data tell me that plumbers can install looped and gridded plumbing/sprinkler systems for well under the cost of two separate systems - while still making a profit. I have listened to all the BS about plumbers not being qualified to install residential sprinklers, and I totally dismiss it. Journeyman plumbers have the same mechanical, pipe fitting and plan reading skills as sprinkler fitters. All they need is training on NFPA 13D or IRC P2904, which a 1- or 2-day class will provide.

I am a proponent of grids. For plumbing fixtures, they eliminate pressure/temperature fluctuations without the need for balancing valves - which require maintenance. Grids save on water because there is less water in the smaller tubing (1/2" v. 3/4-1") that needs to be flushed until the water at the fixture reaches the desired temperature. A key advantage of grids is their hydraulic efficiency. The water distribution pipe can supply sprinklers without exceeding the velocity limits in the plumbing codes. The low velocity in the pipe sections reduces friction loss, so grids can supply the required minimum pressure for lo-flow showerheads without resorting to adding a run of larger diameter pipe to the fixture.

But the biggest reason that the availability of HYDRACAD-R is heartening is that designers like our friend sprinklertech can do plans and calcs independent of the current plumbing suppliers. Each supplier promotes its own version of combined plumbing/sprinkler systems, but independent designers will be able to match designs with local needs. If a combined system will pass muster in your area without backflow prevention, there is a design for that. That is an advantage in areas with high pressure. At the other extreme, designers can provide systems with all potable water that eliminate the need for backflow preventers and do not exceed velocity limits for the plumbing. And finally, the increased number of designers will be able to support the expansion of of the market for plumbers.


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## sprinklertech (Oct 24, 2010)

Paddy said:


> The low velocity in the pipe sections reduces friction loss, so grids can supply the required minimum pressure for lo-flow showerheads without resorting to adding a run of larger diameter pipe to the fixture.


I am aware there are velocity limits on plumbing and I thought some might be surprised to learn there aren't any velocity limits set by the NFPA standards.

25 and even 30 fps is common.

But there are a few insurance underwriters, particularly FM Global, that require velocities to be below 20 or 25 fps. It's one of these things, if I have a grid and everything is below 22 fps with the exception of one pipe which has 28 fps they'll let that one go through.



> But the biggest reason that the availability of HYDRACAD-R is heartening is that designers like our friend sprinklertech can do plans and calcs independent of the current plumbing suppliers. Each supplier promotes its own version of combined plumbing/sprinkler systems, but independent designers will be able to match designs with local needs. If a combined system will pass muster in your area without backflow prevention, there is a design for that. That is an advantage in areas with high pressure. At the other extreme, designers can provide systems with all potable water that eliminate the need for backflow preventers and do not exceed velocity limits for the plumbing. And finally, the increased number of designers will be able to support the expansion of of the market for plumbers.


HYDRACAD-R is an excellent program but there are others as well.

I prefer HASS by *HRS Systems*. which produced *HassHouse* which was specifically designed with residential systems in mind.

Not trying to sell one over the other but I favor HRS Systems only because I've been using it since 1985.

HYDRACAD-R or HassHouse are not easy programs to learn, you are all smart enough but don't think you will be able to sit down and master it over a weekend or even two or three weekends. 

Seems to me a lot of states have gone the right direction in developing licenses designed for plumbers to install sprinklers in one and two family dwellings but what about the design?

Most mechanical and plumbing engineers are not qualified to design sprinkler systems and they don't do it. Sometimes they may show where the supply line comes into the building, or even a circles and lines drawing, but if you look at the drawings and specs there's always a disclaimer that final design is up to the sprinkler company and most states require a sprinkler company to have in their full time employ (this is good for me, it insures I stay employed:thumbsup "Responsible Managing Employee" or RME.

Rules vary from state to state, some states require the license holder to take a course and others, like Texas, require an RME.

I won't sugar coat it, this is going to be tough in Texas.

Requirements for *Texas can be found here*.

For one and two family dwellings



> Responsible Managing Employee-Dwelling
> (RME-D)
> An RME-D licensee is permitted to plan, sell, install, maintain, service, and certify all parts of a one- or two-family dwelling fire sprinkler system (*This licensee must pass the NICET Sprinkler Layout Level II test*, the Sprinkler Dwelling TFM09 test and the Sprinkler Statute & Rules TFM08 test


Passing the NICET test will be a major stumbling block.

*http://nicet.org/*

and specifically for sprinklers

*http://www.nicet.org/candidates/programs/sprinkler.cfm*

From the detail manual *http://www.nicet.org/nicetmanuals/firespk.pdf*



> Level I is designed for entry-level technicians with very limited relevant work experience in the technical subfield. *The Institute recommends that persons with eighteen or more months of relevant work experience set their initial certification goal at Level II.* Certification at Levels II, III, and IV does not require prior certification at a lower level. The Examination Requirements Charts show how many elements must be passed to meet the exam requirement for Levels I, II, III, and IV.


For an RME dwelling you need Level II. 

This is not an easy test and most, if not all, questions will be over NFPA #13 and not #13R.

One just doesn't sign up to take the test. The application requires a verifier sign off that the applicant has knowledge and experience in the element to be tested. Verifiers have to be a professional engineer or holder of a NICET III or IV certificate. 

Maybe I am missing something but it appears to hold a license to install sprinklers in one and two family dwellings the firm must have in their employ someone who passed the requirements for NICET II.

I don't like the way Texas has this set up at all, a superior method is like the one in South Carolina. Someone who might do a dozen systems in a year can't afford to comply with the requirements. A NICET II will most likely be paid in the range of $40k and he is going to be in the form of a book worm; if you hired me don't expect me to go out and start hanging pipe because I won't. I suck at it. I've been designing systems for 35 years, I can give details on everything but I couldn't put a thread on a 1" piece of pipe if my life depended on it. Talk about a worthless field employee it would be me.

In my opinion for 1 and 2 family dwellings all this is not necessary and will only increase the costs substantially.


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## Paddy (Sep 2, 2011)

*Been meaning to reply*

I meant to reply to your post earlier, but I am focusing on my soon-to-be-announced seminar on plumbing-based fire protection. The one-day class dispels the myths about why sprinklers cannot/should not be installed on water distribution pipe, why plumbers cannot/should not install them and related misguided information. It also documents how water distribution pipe can supply the higher volumes to sprinklers without violating the velocity limits for plumbing fixtures. 

Another seminar highlight is the subject of backflow preventers. Two pipe layouts that technically meet the definition of "multipurpose" in NFPA 13D and IRC P2904 have lots of standing water. When water purveyors see that, they won't turn on the water until a backflow preventer is installed. Some of them demand RPZ preventers which increase costs and require annual testing by certified technicians. The seminar will cover two pipe layouts that eliminate standing water - flexible loops and manifolded grids.

One quick question about HaasHouse. Does it calculate manifolded grids? If it does, I want to mention that in my seminar.


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## bml (Feb 8, 2011)

sprinklertech said:


> ............
> 
> Passing the NICET test will be a major stumbling block.
> 
> ...



What are the necessary steps in obtaining NICET certification? I'm a thirteen year sprinkler fitter, and I'm interested in career advancement. Years ago, I worked in the design department of a sprinkler contractor, but only briefly. I've contemplated several different career paths, including design, inspections or a field superintendent, but I'm leaning more toward design. Is it possible to hold NICET certification in both inspections and as a layout tech??


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## Paddy (Sep 2, 2011)

> My question is, are there any parts of a residential or commercial bldg that gets extra sprinkler head placement, or are all areas equal and therefore sprinkler head spacing equal in all parts of a bldg?


Tommy:

I recently joined this forum. I did not see an answer to your question and thought that I would respond, albeit a long time after your post.

When it comes to fire sprinklers, spacing and density per sprinkler are important. Sprinkler spacing varies in both residential and other occupancies. (When I say residential, I am referring to 1- and 2-family dwellings.) Sprinkler volume per square foot of coverage varies in non-residential occupancies. It does not vary in dwellings.

NFPA 13, the national standard for sprinkler installation, categorizes occupancies by Hazard Class. In non-residential occupancies, sprinkler spacing, area covered and volume per square foot vary from Light Hazard to Special Hazard.

The sprinkler installation standards consider 1- and 2-family homes to be Light Hazard occupancies. For these occupancies, NFPA 13D and the International Residential Code section P2904 require a sprinkler volume of 0.05 gpm per square foot of coverage. Manufacturers of residential sprinklers offer sprinklers that will deliver that volume over 12' X 12' to 20' X 20' areas. The only difference between them is the pressure needed to provide the 0.05 gpm per square foot coverage.

Typically, a 12' X 12' coverage requires between 7-8 psi at the sprinkler. A 16' X 16' coverage requires around 10 psi. The largest area allowed for residential sprinkler coverage, 20' X 20,' requires over 20 psi.

There is another big difference between sprinkler coverage for dwellings and non-residential occupancies. The residential standards require less water. The requirement in NFPA 13 for Light Hazard occupancies requires a minimum of 0.05 gpm over a 1500 square foot area. The two residential installation standards, IRC P2904 and NFPA 13D, require 0.05 per square foot for a maximum of two sprinklers. 

The difference? The installation standards for dwellings require tens of gpm instead of hundreds - and they only require a 7-10 minute supply.

Paddy


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