# sizing gas piping



## winslow

Was never really that profocient at sizing gas piping, I understand the sizing charts in the UPC but when I use them they seem to recommend undersized piping. Was hoping someone who does a lot of sizing gas lines could help.

Here in Hawaii we use SNG with a specific gravity of .675 and a heat value of 1050. We also use LPG with a specific gravity of 1.5 and a heat value of 2520.

Running a gas line for a commercial kitchen with a developed lenth of 65 feet and a demand of 400,000 btu. The demand on nat would be 381 CFH. According to the charts in the UPC this would require an 11/4 trunk line. 
Using LPG would give me a demand of 159 CFH, which would require a 1" trunk line. Are these values good or are they undersized? What reference do you use when sizing gas lines?


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## drtyhands

UPC 
Sized,Drawn,Submitted to authority,approved,installed.
Miles of it.


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## winslow

drtyhands said:


> UPC
> Sized,Drawn,Submitted to authority,approved,installed.
> Miles of it.


 
So those sizes in my original post look OK to you then? just curious.

The problem seems to be that when architects and engineers put anything on paper nowadays they oversize/ overkill everything.


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## ROCKSTARPLUMBER

Those sizes seem accurate if you want to run those size lines. Why not use a higher lb pressure, and run a smaller line and regulate? Tha's how we does it in the south.:thumbsup:


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## drtyhands

winslow said:


> So those sizes in my original post look OK to you then? just curious.
> 
> The problem seems to be that when architects and engineers put anything on paper nowadays they oversize/ overkill everything.


 Your code book tells you how to size gas.
You should be carefull with engineers drawing your plumbing.Just because the city approves what he draws does not make it legal.One needs to understand the code and make adjustments.It will help you cut your bid down substantialy when sized properly if the engineer has overkill.
A plan checker does not have the same knowledge/experience as a field inspector.


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## drtyhands

ROCKSTARPLUMBER said:


> Those sizes seem accurate if you want to run those size lines. Why not use a higher lb pressure, and run a smaller line and regulate? Tha's how we does it in the south.:thumbsup:


In the past I've seen others post pictures of regulators without venting to outside atmosphere.Is that legal?
How much are regulators?


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## ROCKSTARPLUMBER

Hell, I dunno, they range in price. They DO make indoor regulators. There are line ones, and appliance ones. Google works wonders.:thumbsup:


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## drtyhands

ROCKSTARPLUMBER said:


> Hell, I dunno, they range in price. They DO make indoor regulators. There are line ones, and appliance ones. Google works wonders.:thumbsup:


Do the regulators need to be vented to satisfy code?

P.S 
Do you know me?


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## SlickRick

Since there is no 65' column, going to 70'- 11/4" would carry 490,000 btu, reducing the size according to btu load, off the same total length column.


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## ROCKSTARPLUMBER

drtyhands said:


> Do the regulators need to be vented to satisfy code?
> 
> P.S
> Do you know me?


I am pretty sure that we use different codes.IPC here. I usually try to research on my own as much as possible before I ask a code question on a public forum. You say you have ran miles of it, you should know. But, being that you are in Cali, I forgive you. There is a simple answer to your question though.


PS. No, I don't know you.


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## user4

I don't agree with a lot of the things in the UPC code, and really have no use for it whatsoever. I use a sizing chart similar to this one, and upsize it one size because that chart is based on the pressure being 21" of WC and the local gas supplier here delivers gas to the building at 7" of WC unless you request something different in writing, and it is subject to their approval.


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## Plumbus

What reference do you use when sizing gas lines?
Assuming Hawaii is using the 2006 UPC, try Table 12-8 for natural gas and for propane it depends on the inlet pressure (see Tables 12-29 thru 12-41).
The regulators I use at the point of entry are set at 11" water column, so I use Table 12-32.
Why not use a higher lb pressure?
With natural gas, higher pressure is not always available from the gas utility. 
All the medium pressure regulators I've installed have to be vented to the exterior of the building?
I don't agree with a lot of the things in the UPC code, and really have no use for it whatsoever.
Unfortunately, those of us in areas subject to the UPC don't have the luxury of choosing which sizing charts they wish to use.


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## drtyhands

ROCKSTARPLUMBER said:


> I am pretty sure that we use different codes.IPC here. I usually try to research on my own as much as possible before I ask a code question on a public forum. You say you have ran miles of it, you should know. But, being that you are in Cali, I forgive you. There is a simple answer to your question though.
> 
> 
> PS. No, I don't know you.


What?
I know I need'em here.
I asked about you...In the south.
I'm not Googleing your code.It's not worth the time and I'm not as good as Utah.
What post count would one have to have before you would feel comfortable with unconditionaly answering a member on a cross code issue?
For those that don't know me...

Adam,
Pleased to meet you.
:jester:

Hey,You guys have more smileys


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## ROCKSTARPLUMBER

The exception to the rule based on the code I use is an approved Vent-limiting device. The regulator must be labeled that such device is in said regulator.


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## ROCKSTARPLUMBER

drtyhands said:


> What?
> I know I need'em here.
> I asked about you...In the south.
> I'm not Googleing your code.It's not worth the time and I'm not as good as Utah.
> What post count would one have to have before you would feel comfortable with unconditionaly answering a member on a cross code issue?
> For those that don't know me...
> 
> Adam,
> Pleased to meet you.
> :jester:
> 
> Hey,You guys have more smileys



Post count means nothing to me. I hate everyone equally until they give me a reason not to.


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## drtyhands

ROCKSTARPLUMBER said:


> Post count means nothing to me. I hate everyone equally until they give me a reason not to.


I like it


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## Plumbus

ROCKSTARPLUMBER said:


> The exception to the rule based on the code I use is an approved Vent-limiting device. The regulator must be labeled that such device is in said regulator.


Didn't know of such a beast. I wonder if it's approved in UPC country. Will find out tomorrow. Wait a minute, what's the point of a vent if you put a throttling device in it?:blink:

I'm comfortable with you, Adam


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## ROCKSTARPLUMBER

Plumbus said:


> Didn't know of such a beast. I wonder if it's approved in UPC country. Will find out tomorrow. Wait a minute, what's the point of a vent if you put a throttling device in it?:blink:
> 
> I'm comfortable with you, Adam


hince the term "limited"


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## Plumbus

Limiting, throttling.... what's the difference?????


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## ROCKSTARPLUMBER

I guess there is no difference in the terms. It's code approved, thats all i need, or care to know.


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## drtyhands

Plumbus said:


> Didn't know of such a beast. I wonder if it's approved in UPC country. Will find out tomorrow. Wait a minute, what's the point of a vent if you put a throttling device in it?:blink:
> 
> I'm comfortable with you, Adam


Thanks


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## ILPlumber

What's wrong with the sizing chart in NFPA 54?

It covers all the common pressure ranges. I have used it on jobs ranging from 1/2" threaded to 8 welded. 

I disagree on bumping the pressure and installing regs. I think were piping diameter can be increased, pressure should be kept low. 

Regs. are pricey. I can run a lot of larger diam pipe as opposed to buying 30 regs and venting them.


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## SlickRick

ILPlumber said:


> What's wrong with the sizing chart in NFPA 54?
> 
> It covers all the common pressure ranges. I have used it on jobs ranging from 1/2" threaded to 8 welded.
> 
> I disagree on bumping the pressure and installing regs. I think were piping diameter can be increased, pressure should be kept low.
> 
> Regs. are pricey. I can run a lot of larger diam pipe as opposed to buying 30 regs and venting them.


I know that's right. When wardflex came out, the gas co. was pushing it. We did a detention center w/medium pressure. The wardflex was free but by the time I installed all the regs. and vents it was a loosing proposition.


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## ROCKSTARPLUMBER

ILPlumber said:


> What's wrong with the sizing chart in NFPA 54?
> 
> It covers all the common pressure ranges. I have used it on jobs ranging from 1/2" threaded to 8 welded.
> 
> I disagree on bumping the pressure and installing regs. I think were piping diameter can be increased, pressure should be kept low.
> 
> Regs. are pricey. I can run a lot of larger diam pipe as opposed to buying 30 regs and venting them.


Regs have their place no doubt. But,other than the risk factor of a potential leak on a higher pressure gas line, why do you like to run the bigger line?

I got into using regs on gas lines lately do to the big BOOM in tankless sales here. This is due to the generous rebates our local city is giving out for them.


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## drtyhands

I was able to cut the price in half on a long roof job that two other contractors failed to consider medium pressure.Took 200' feet of 4" and cut it down to 1-1/4".The big gas draw was at the end of the run.The gas co. swapped out the meter for free.
Having General Motors buy the regs with the equipment helped me out.I told them it would be a lot less weight on the roof to move them in the proper direction.


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## user4

drtyhands said:


> I was able to cut the price in half on a long roof job that two other contractors failed to consider medium pressure.Took 200' feet of 4" and cut it down to 1-1/4".The big gas draw was at the end of the run.The gas co. swapped out the meter for free.
> Having General Motors buy the regs with the equipment helped me out.I told them it would be a lot less weight on the roof to move them in the proper direction.


Who holds the liability when the reg fails?

How comfortable are you with leaving a gas line w/ 28" or more of water column exposed on a roof where it can get damaged by any roofer, handyman, satelite installer , whatever?

I would prefer to minimize the pressure at the lowest possible point, at 2 PSI a gas leak blowing wide open will blow the building up in no time if ignited, and if it is near a vent stack it takes little atmospheric pressure to draw it into the building.


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## drtyhands

Killertoiletspider said:


> Who holds the liability when the reg fails?
> 
> How comfortable are you with leaving a gas line w/ 28" or more of water column exposed on a roof where it can get damaged by any roofer, handyman, satelite installer , whatever?
> 
> I would prefer to minimize the pressure at the lowest possible point, at 2 PSI a gas leak blowing wide open will blow the building up in no time if ignited, and if it is near a vent stack it takes little atmospheric pressure to draw it into the building.


The regs belong to them.That's another beauty of it.
No,I do not have a problem with medium pressure gas contained inside a schedule 40 steel pipe...None.
It's some pretty tough stuff Spider.I'll stick with it.I work with it on a regular basis.We got some BIIIG areas to get gas around to(properties and structures).Really helps out when the meter is on the street on the city's side of the gate and the house is 300' up the driveway.Hate to see someone have to run 4" through the house to the kitchen(small exaggeration).

I did the penthouse on one Utah's highrises he's a witness on.He saw it.It has some 50 1/2" gas services on P1 serving all units going all the way up 23 floors to where the csst vented regulator is installed in the penthouse.


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## Tankless

Well, I asked about why there was no medium to high pressure gas systems around here and the inspector simply said, this is earth quake country and the powers that be didn't want high pressure gas running in peoples homes. An earth quake feels sorta like sitting down on a water bed for about 5 to 10 seconds. When the Northridge quake hit, Balboa Blvd whis is a 6 lane regular road was split open and a high pressure line blew apart and had flame shooting in the air. The water main also let go...it was pretty bad and I grew up about 5 minutes away from that. They left tha gas on, until Clinton could come and see it. He got out of his limo, waved to all of us with a big smile and then left. Fing tard.

If you're so inclined to know why we have SO many building codes and insane safety codes in place in the UPC and other trades' code, you can read what I lived through. This one did not feel like sitting on a water bed. It felt like sitting on a dunk tank bench and some kid hitting the bulls eye, with no water in the tank 


http://www.ci.la.ca.us/lafd/eq.htm



> Also significant were the ruptures of a large natural gas main and a water main at the intersection of Balboa and Rinaldi. These ruptures occurred immediately following the earthquake.
> Subsequent to the rupture, the natural gas main ignited, and five single family homes were consumed in the ensuing fire.
> Area residents were evacuated by arriving firefighters and no serious injuries were reported.


http://scec.gps.caltech.edu/recenteqs.html


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## Plumbus

Did some homework on the vent limiting device. 
Per UPC
C. Uniform Plumbing Code IAPMO/ANSI UPCI-2003 section _"1209.7.5 Venting (A) Line Gas Pressure Regulators._ 
(1) An independent vent to the outside of the building, sized in accordance with manufacturer's instructions, shall be provided where the location of a regulator is such that a ruptured diaphragm will cause a hazard. Where there is more than one regulator at a location, each regulator shall have a separate vent to the outside, or if approved by the Authority Having Jurisdiction, the vent lines shall be permitted to be manifolded in accordance with accepted engineering practices to minimize back pressure in the event of diaphragm failure. [See NFPA 54:5.9.7] for information of properly locating the vent.) Materials for vent pipes shall be in accordance with Section 1209.5. 
* Exception:* A regulator and vent-limiting means combination listed as complying with ANSI Z21.80 / CSA 6.22 Standard for Line Pressure Regulators shall be permitted to be used without a vent to the outdoors. 

http://www.maxitrol.com/ventlimiter.html
Seems they are limited in their BTU load. As explained to me, they are generally used in a single appliance application (not whole house). 

The danger of a sub regulator going bad is no greater than that for the regulator supplied by the gas utility. Worst case scenario is a ruined appliance gas valve.


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## jeffreyplumber

*gas sizing*

Using UPC tables @.60 specific gravity and 1100 btu per cubic foot this is our basic for natural gas . our chart is in 10 ft increments so 70 foot alows 490 cfh or 539000 btu on 1 1/4 pipe. As far as medium presure with a regulator at the appliance not very common here Its done on some jobs it would take a little research . Not a great saving on a job of this caliber.


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## Plumbus

jeffreyplumber said:


> Using UPC tables @.60 specific gravity and 1100 btu per cubic foot this is our basic for natural gas.


I know that fig. 12-2 says to divide BTU's by 1100 to calculate cubic feet, but some utilities are supplying gas rated at 1050 btu's per cubic foot or less. I think it's safer to devide by 1000. Easier too.


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