# GPM Calculator



## Retire09 (Jan 7, 2011)

How can I determine the approximate GPM I could expect from a 1" copper line, 100' long at 60PSI? Is there a chart or equation for this?


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## plumbpro (Mar 10, 2010)

In the back of my code book


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## Protech (Sep 22, 2008)

Retire09 said:


> How can I determine the approximate GPM I could expect from a 1" copper line, 100' long at 60PSI? Is there a chart or equation for this?


The wording you use makes me think you are not a licensed plumber.


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## Protech (Sep 22, 2008)

when you say 60 psi, are you talking about the inlet side of the pipe or the outlet side? 
what is the accepable pressure drop cross the pipe at said flow rate?


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## Hillside (Jan 22, 2010)

The easiest way to do it is get a bunch of homeowner depot 5 gallon buckets and have someone crank it on and fill as many as u can in 1 min that should get u to where u need to be, ( rough estimate of course) good luck!! :laughing:


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## Protech (Sep 22, 2008)

HillsidePlumbco said:


> The easiest way to do it is get a bunch of homeowner depot 5 gallon buckets and have someone crank it on and fill as many as u can in 1 min that should get u to where u need to be, ( rough estimate of course) good luck!!


yeah that will work, at 0 flow pressure.....


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## Lifer (Nov 23, 2010)

Protech said:


> The wording you use makes me think you are not a licensed plumber.


 

Come now , he said copper and psi ( a few times ) .. I think he's a great plumber he even said GPM .. not tub full's or Pail fulls.. lets cut him some slack ..

LOL .. I am only kidding . But honestly I do not know how to solve this problem either it may be in my code book as well. But that's down stairs and I am not .


Lifer...


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## SlickRick (Sep 3, 2009)

Retire09 said:


> How can I determine the approximate GPM I could expect from a 1" copper line, 100' long at 60PSI? Is there a chart or equation for this?


An intro is requested from all new members. In case you missed it, here is the link. http://www.plumbingzone.com/f3/.

The PZ is for Plumbing Professionals ( those engaged in the plumbing profession)

Post an intro and tell our members where you are from, yrs in the trade, and your area(s) of expertise in the plumbing field.

This info helps members who are waiting to welcome you to the best plumbing site there is.

We look forward to your valuable input.
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## Pipe Dreams (Feb 10, 2011)

Retire09 said:


> How can I determine the approximate GPM I could expect from a 1" copper line, 100' long at 60PSI? Is there a chart or equation for this?


It's about 50 GPM


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## Protech (Sep 22, 2008)

I'm trying to think of the situation in the plumbing industry where question like that would even be relevant


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## Pipe Dreams (Feb 10, 2011)

Protech said:


> I'm trying to think of the situation in the plumbing industry where question like that would even be relevant


Sprinkler Systems possibly....A homeowner who wants to know how fast their bathtub is going to fill (better mention I'm kidding before I end up as someone's signature)


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## Protech (Sep 22, 2008)

Pipe Dreams said:


> Sprinkler Systems possibly....A homeowner who wants to know how fast their bathtub is going to fill (better mention I'm kidding before I end up as someone's signature)


those examples all require a flow pressure calculation whereas his question does not.


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## Pipe Dreams (Feb 10, 2011)

Protech said:


> those examples all require a flow pressure calculation whereas his question does not.


How does GPM not give you how fast something will fill with water? A 50 Gallon drum being filled @ 50 GPM will fill in 1 minute last time I checked. I don't care if it's a smaller pipe filling it with more pressure or a bigger pipe with less pressure and more volume....the end result is the same if the GPM is equal.


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## 6th Density (Nov 29, 2010)

I would definitely call a plumber and figure out what kind of copper is in use and if it's new or existing pipe.
There's a start.


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## Redwood (Sep 8, 2008)

I used to figure that stuff out all the time... :laughing:


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## markb (Jun 11, 2009)

Redwood said:


> I used to figure that stuff out all the time... :laughing:



lol


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## Protech (Sep 22, 2008)

And when would that sort of calculation be needed in plumbing?

Break it down for me please.



Pipe Dreams said:


> How does GPM not give you how fast something will fill with water? A 50 Gallon drum being filled @ 50 GPM will fill in 1 minute last time I checked. I don't care if it's a smaller pipe filling it with more pressure or a bigger pipe with less pressure and more volume....the end result is the same if the GPM is equal.


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## breid1903 (Feb 8, 2009)

homeowner depot buckets hold less than 5 gal, but more than 4. breid............:rockon:


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## Retire09 (Jan 7, 2011)

Let me explain. I am the building inspector in a small community in Alaska. We are considering the possibility of adopting the 2009 IRC which requires sprinkler systems in single family homes. State statute will allow a home owner to do his own work on his own home. If adopted, I will have to review the plans, add what is missing, correct what is wrong, issue a permit and then inspect the systems along with everything else in the house for substantial compliance with all codes and NFPA 13D. I have an existing 3/4" tap to the city 6" main that has no meter that can be increased to a 1" or 11/4" service line to the house. The tap is copper. The service line is HDPE and the houses are typically done in PEX. I need 26 GPM at the most remote head in the house. The total developed length of this from the tap may be 125'. The city pressure is a little over 60PSI at the end of the tap.
I have been doing combination inspections for over 20 years including plumbing but my specialty is electrical.
If I am going to enforce this code I need to know how to determine when its right. I'm just trying to get up to speed on this. Any help will be appreciated.


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## Protech (Sep 22, 2008)

Then you will need to do the hazen-williams equation to find the answer as you need the water coming out of the heads to be under pressure.

I don't do fire sprinklers, but let's say you need each heads to spray at 30PSI. Each head flows at 5 GPM and you have 10 heads so you have 50gpm of demand. If your incoming static pressure is 60 PSI that means you have to design a system with a friction loss at the end of the longest run of 30 PSI or less.

You will have to do the hazen-williams equation for the given flow on each leg of the system and design it accordingly.

It is not anywhere as simple as how you phrased the question in the original post. Each system will have to be evaluated by a master plumber capable of doing said calculations or a mechanical engineer.





Retire09 said:


> Let me explain. I am the building inspector in a small community in Alaska. We are considering the possibility of adopting the 2009 IRC which requires sprinkler systems in single family homes. State statute will allow a home owner to do his own work on his own home. If adopted, I will have to review the plans, add what is missing, correct what is wrong, issue a permit and then inspect the systems along with everything else in the house for substantial compliance with all codes and NFPA 13D. I have an existing 3/4" tap to the city 6" main that has no meter that can be increased to a 1" or 11/4" service line to the house. The tap is copper. The service line is HDPE and the houses are typically done in PEX. I need 26 GPM at the most remote head in the house. The total developed length of this from the tap may be 125'. The city pressure is a little over 60PSI at the end of the tap.
> I have been doing combination inspections for over 20 years including plumbing but my specialty is electrical.
> If I am going to enforce this code I need to know how to determine when its right. I'm just trying to get up to speed on this. Any help will be appreciated.


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## Protech (Sep 22, 2008)

Also, if you are asking only about the service pipe going to the building, you would still need to know how much flow-pressure will be require for the system it feeds.

Hypothetical example: 1" copper line, 100' long at 60PSI at the begining of the run. 

At 20gpm you will lose 12.4 psi across the water service.
25gpm=18.8PSI Since you started at 60PSI, you end up at 41.2PSI
30gpm=26.3PSI Since you started at 60PSI, you end up at 33.7PSI
40gpm=44.8PSI Since you started at 60PSI, you end up at 15.2PSI

Obviously, you are getting into trouble at anything over 30 gpm with the above parameters.


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## Redwood (Sep 8, 2008)

This is one of those situations where an into would have saved you some heat... :laughing:

You might ask one of the mods to move the thread over to the Fire Suppression Systems section. Maybe SprinklerTech will pick up on it and give you some schooling. He can no doubt get you pretty proficient in the field...


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## Protech (Sep 22, 2008)

Also, many codes will not allow water velocity in copper pipe to exceed 5fps. In lite of this, you won't be able to get more than 12 gpm out of a 1" copper pipe.


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## easttexasplumb (Oct 13, 2010)

100' of 1" copper will cost me $500.00


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## OldSchool (Jan 30, 2010)

Protech said:


> I'm trying to think of the situation in the plumbing industry where question like that would even be relevant


There would be many situations...

Apartment buildings for one....

Commercial complexs 

food processing plants

Industrial applications

and many many more


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## Protech (Sep 22, 2008)

OldSchool said:


> There would be many situations...
> 
> Apartment buildings for one....
> 
> ...


Could you explain how that would apply to an apartment building as any situation in said building would involve a flow-pressure calculation?


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## OldSchool (Jan 30, 2010)

Protech said:


> Could you explain how that would apply to an apartment building as any situation in said building would involve a flow-pressure calculation?


In a multi apartment complex or high rise.... you would want to know at least the GPM that can be distributed through any given water main or riser to accomadate a certain % of overall use.


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## PLUMBER_BILL (Oct 23, 2009)

easttexasplumb said:


> 100' of 1" copper will cost me $500.00


 
That was yesterdays price. ...... LOL


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## Protech (Sep 22, 2008)

OldSchool said:


> In a multi apartment complex or high rise.... you would want to know at least the GPM that can be distributed through any given water main or riser to accomadate a certain % of overall use.


Yes but, again, that would involve a flow-PRESSURE calculation which is not the type of calculation the OP was asking about.

I'm starting to sound like a broken record. Sheesh.


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