# Natural Gas Pipe Sizing



## azheat112 (May 19, 2012)

Not sure if this has been asked before but I am confused on the low pressure gas equation in the UPC and also the Internation fuel gas code. I have a job that has 7 inch water column with a 3" meter. I have 300' longest length and I need to squeeze a little more than the spreadsheet will give me on the 5 inch water collumn spread sheet. The spreadsheet on (IFGC) 402.4(2) I have 1,800 Capacity in cubic feet of gas per hour. I need 1,880 to acomodate the new heaters on the job we are bidding. The equation is going to look weird typed but ill give it a shot. Schedule 40 Metallic pipe

D= Q*.381/ 19.17(^H/Cr*L).206

are the numbers .381 and .206 exponents?


Jared


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## TX MECH PLUMBER (May 27, 2011)

When you finally come with a question you come with a good one. !!! A bit out of my area do you not have a master p around to help ??

Welcome to the zone


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## azheat112 (May 19, 2012)

no, I was actualy thinking about calling the City Inspector and seeing if the Plumbing Inspector could help me out. He might, he might not, I should try it before I tell the G.C. this will work... I almost think it would have to work if 5 inch Water column is 1800 and I need 1,880 and I have 7 inch water column but I need to put a little science on it instead of just winging it as much as I want to.


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## TX MECH PLUMBER (May 27, 2011)

That's smart My name is ...

Jarrad. I go by jay tho. 

Some one will come along with answers soon!!!


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## rjbphd (Feb 5, 2010)

TX MECH PLUMBER said:


> That's smart My name is ...
> 
> Jarrad. I go by jay tho.
> 
> Some one will come along with answers soon!!!


 Jay??? Like jaaaaazzzzddddaaaq?


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## rjbphd (Feb 5, 2010)

azheat112 said:


> Not sure if this has been asked before but I am confused on the low pressure gas equation in the UPC and also the Internation fuel gas code. I have a job that has 7 inch water column with a 3" meter. I have 300' longest length and I need to squeeze a little more than the spreadsheet will give me on the 5 inch water collumn spread sheet. The spreadsheet on (IFGC) 402.4(2) I have 1,800 Capacity in cubic feet of gas per hour. I need 1,880 to acomodate the new heaters on the job we are bidding. The equation is going to look weird typed but ill give it a shot. Schedule 40 Metallic pipe
> 
> D= Q*.381/ 19.17(^H/Cr*L).206
> 
> ...


Intresting.. ya better of going straight to gas company engineer than going to inspector that claimed to know it all.


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## mightypipe (Dec 22, 2012)

TX MECH PLUMBER said:


> When you finally come with a question you come with a good one. !!! A bit out of my area do you not have a master p around to help ??
> 
> Welcome to the zone


Ha ha... AZ does not have an MP lic.
Only Phoenix even has a JP card.


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## mightypipe (Dec 22, 2012)

azheat112 said:


> no, I was actualy thinking about calling the City Inspector and seeing if the Plumbing Inspector could help me out. He might, he might not, I should try it before I tell the G.C. this will work... I almost think it would have to work if 5 inch Water column is 1800 and I need 1,880 and I have 7 inch water column but I need to put a little science on it instead of just winging it as much as I want to.


Call planning and development at 602.262.7811. Talk to a plan reviewer. They are always helpful.


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## justme (Jul 4, 2012)

Let me ask u a question what pressure is behind the meter ? Why can't the gas company turn the regulator up? Talk to the gas company.


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## plbgbiz (Aug 27, 2010)

rjbphd said:


> Intresting.. ya better of going straight to gas company engineer than going to inspector that claimed to know it all.


^^^ What he said. :yes:


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## johnlewismcleod (Apr 6, 2012)

You're approaching this problem from an odd angle, Jay.

Pipe size, available BTU's at the meter, and needed BTU's in the building should be all you need to calculate anything. Modifying any of those variables should get it done for you.

Maybe I'm just not understanding the question, though :blink:


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## UN1TED-WE-PLUMB (Oct 3, 2012)

He's thinking the higher pressure will give him what he needs. 

Most residential fixtures have a max input of 5" wc. This sounds like a commercial application. 

He needs to check the rating plates on the fixtures to see if they can operate at the higher pressure. 

Did you verify your pressure with a manometer? You will usually have 8" or so at the meter but by the time it makes it to the fixture it will normally be around 5" due to pressure drop.


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## azheat112 (May 19, 2012)

You guys know your gas lol, I'm going to use my ask the audience lifeline and call the gas company to give me some more volumn. Thanks guys I was trying to overthink it.


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## UN1TED-WE-PLUMB (Oct 3, 2012)

More volume only comes with larger pipe. 

You need to check your pressure with a manometer and check the rating plates on the fixtures to see max input pressure to see if you can raise the pressure effectively. 

You could always run a dedicated line to your waterheaters so long as your meter can handle the extra load. They may need to upgrade the meter. Just depends. 

I'm not sure of the gas company will be much help.


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## UN1TED-WE-PLUMB (Oct 3, 2012)

Ya know the best way would probably be to have the gas co split the meter and run a 2 psi dedicated line to your water heaters. 

It sounds like the low pressure system is maxed out.


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## azheat112 (May 19, 2012)

what about the gas company changing a regulator with a less restrictive oraface to give me more volume without pressure increase?


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## UN1TED-WE-PLUMB (Oct 3, 2012)

That may work but honestly I've never had any experience with that before. Maybe someone who has can chime in.

I always pursue another method.


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## Gettinit (May 9, 2012)

azheat112 said:


> what about the gas company changing a regulator with a less restrictive oraface to give me more volume without pressure increase?


I have done it but only after talking to their engineers. They will not do it unless an engineer signs off. A fraction of an inch can really help in certain instances. You need to know exactly what it is you have and need before calling or they will blow you off.


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## azheat112 (May 19, 2012)

called the gas company, they said they will upgrade the meter to whatever the new demands are at no cost to the customer. They seemed really helpful, once it passes inspection they said they will come out and make sure its got enough gas comming in.


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## Gettinit (May 9, 2012)

azheat112 said:


> called the gas company, they said they will upgrade the meter to whatever the new demands are at no cost to the customer. They seemed really helpful, once it passes inspection they said they will come out and make sure its got enough gas comming in.


If they charge it is usually when you are downgrading. This way is really the easiest way to do it.


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## Epox (Sep 19, 2010)

azheat112 said:


> what about the gas company changing a regulator with a less restrictive oraface to give me more volume without pressure increase?


They've done that for me.


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## BigDave (Mar 24, 2012)

azheat112 said:


> what about the gas company changing a regulator with a less restrictive oraface to give me more volume without pressure increase?


If I understand your question...
As long as your existing piped system will deliver the btu load to your
appliances (additions included), an increase in pressure should not
be needed. A simple request to the gas company, for a larger capacity
(CFH) meter should do the trick.


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## jeffreyplumber (Dec 7, 2009)

Im alittle confused by your question.. Are you under upc code ? If so then you are allowed at 300foot 1810 cu ft demand on a 3 inch line . If your demand is greater than that you must go bigger on pipe size you can change regulators put bigger meters till your blue in the face but if you are undersized you are undersized. Changing to medium pressure may be an option. as is getting the inspection department and or gas suppliers blessing because it is such a slight undersize


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## UN1TED-WE-PLUMB (Oct 3, 2012)

What he said^^

A larger capacity meter will do nothing if your pipe will not meet the demand. 

My vote is on a dedicated 2 psi line directly to your waterheaters. 

The guys at the gas company are usually a bunch of lazy idiots.


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## score300 (Feb 1, 2013)

Depending on how many fixtures you have attached to the system, I would consider changing the whole system to a 2lb system and putting regulators where needed. I do that frequently on Papa Johns interior build outs.


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## johnlewismcleod (Apr 6, 2012)

5.5 inches is too low...something's out of balance in the system.

It could be the pipe size is too small to deliver the load demand (friction loss) or the regulator at the meter is too small and needs to be replaced with a higher BTU unit.

You won't know which it is until you tally the load and look at the pipe size and layout (it could be just the branch your heaters are on that is undersized).

Once you know what they have the fix will be clear.

United's approach would get you what you need for your heaters, but leave the rest of the system under-pressured.


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## jeffreyplumber (Dec 7, 2009)

I wouldnt be be too worried about having 70 or 80 cu ft demand over the max on a 3 inch line as far as it being a proper working system. its just that you arent meeting code. But what does upc code and ipc have to do with each other ? I know upc and thats the only code Ive used here in sizing gas. I cant choose a code


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## azheat112 (May 19, 2012)

the boss says we should be good as long as it is engineered. If they make us go 4" at the meter it wont kill us, I have it figured to bring the piping all the way back to the meter and tee there as it is because non of the branches will support the new fixtures. He said the plumbing code is a little overkill on the sizing and an engineer can overrule the code. I will give you guys a follow up after we do it. I'll let you know if I get a green tag on a 3" pipe with 1880 CFH on it. thanks for all of the input.


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## jeffreyplumber (Dec 7, 2009)

How has it worked out? Your just barely undersize of course it will work just fine. just wondering who is holding you back building dept, gas co or you not wanting to go outside the code and be responceable (understandable) ?


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## azheat112 (May 19, 2012)

talked to the GC on the project said the owners dont want to do the add on any more for the heaters. You are right about not wanting to be responsible for going outside of the code I would not do it unless it is engineered, taking the responsiblitiy off our plate (for the most part). I wish we could have done it to see how it went throught the engineering, building dept and inspection phase. Sorry to leave you guys hanging on this one, kind of funny had a lot of different opinions on weather our idea would fly or not. Thanks for the feedback, hopefully next time I have a tough question I can do the project to give you guys feedback.


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## Plumbus (Aug 4, 2008)

Some good suggestions here, especially to increase to medium pressure (2 psi). 
I may have an easier solution. Did you figure your CFH demand by dividing total BTU's by 1000? If so, ask your gas supplier the btu value of a CFH of their NG? If it's more than 1000/cfh you can adjust your divisor and come up with a larger result (ie. more cfh's). Is your run exactly 300' or is it somewhere between 250' and 300'? If it is, you can play with the numbers in Table 12-8 accordingly, which may also allow you to claim a delivery of over 1080 cfhs.


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## Greenguy (Jan 22, 2011)

Not sure about code there, but when I lived in BC I believe anything over 2-1/2" had to be pressure welded, which can add costs, also you may consider running 2" lines with 5 psi gas then branch off with step down regs as needed. Sorry still trying to learn the codes down here.


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