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Old 07-11-2016, 04:55 PM   #1
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Gas pipe sizing, plumber says 3/4" is big enough...


Hi all, so I normally do my own work around the house, but we just bought a new house and decided to just hire out running a gas line for a stove because I am swamped with the move and prepping the old house for sale. Unfortunately, I have had bad luck with contractors doing poor work, that's why I just started doing everything myself.

Well today, the plumbing company came out to check out the project. I thought we would need to upgrade the gas line from the meter from 3/4" inch to 1 1/4" in order to add our stove. The plumber wanted to just run another 1/2" line off the existing 3/4" line instead and said it wouldn't be a problem. I just want a second opinion as I am no expert here, and he is supposedly. Can someone take a look at this diagram and provide your input? This is for natural gas and I have seen a dozen or so charts that don't indicate the pipe size is large enough. This company is pretty big around here, well reputed and all employees are licensed plumbers, so I am not sure if I should just roll with it?

I should note that I calculated the BTU of the stove by just adding up all burners. Hope thats right.

Here's the project. All elbows in the 3/4" line are shown, its harder to show them in the 1/2" line because of the 2d nature of the drawing, so I just state how many fittings there are.

Last edited by gtzpower; 07-11-2016 at 05:05 PM. Reason: image didn't work
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Old 07-11-2016, 06:37 PM   #2
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Re: Gas pipe sizing, plumber says 3/4" is big enough...


https://www.google.com/url?sa=t&rct=...VQdlsA&cad=rja

Gas pipe sizing chart PDF File

Don't forget to count the fittings but it looks undersized at a quick glance to me.

Last edited by Ghostmaker; 07-11-2016 at 06:39 PM.
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Old 07-11-2016, 09:32 PM   #3
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Re: Gas pipe sizing, plumber says 3/4" is big enough...


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Originally Posted by Ghostmaker View Post
https://www.google.com/url?sa=t&rct=...VQdlsA&cad=rja

Gas pipe sizing chart PDF File

Don't forget to count the fittings but it looks undersized at a quick glance to me.
Thanks for the reply. This is actually the same chart I found on google and have been primarily using.

At a quick glance, you can see that we have 165k total BTU. 3/4" only supports 160 BTU at 20 feet, which says to me that we are WAY outside of the realm of what this chart says would be okay, not even counting fittings. I just wondered if I was doing it wrong or if I should question their advice. Thanks for the reply.

Last edited by gtzpower; 07-11-2016 at 09:33 PM. Reason: grammar
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Old 07-11-2016, 11:23 PM   #4
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Re: Gas pipe sizing, plumber says 3/4" is big enough...


You need to confirm the supply pressure before you say to upside.

A quick call to your gas company will tell you this....or you can measure the pressure.

In some cases the gas company will up the pressure a little if necessary
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Old 07-12-2016, 07:23 AM   #5
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Re: Gas pipe sizing, plumber says 3/4" is big enough...


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In some cases the gas company will up the pressure a little if necessary
How is that possible on a individual basis or even at all?
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Old 07-12-2016, 08:40 AM   #6
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Re: Gas pipe sizing, plumber says 3/4" is big enough...


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How is that possible on a individual basis or even at all?
I wondered about how a 3/4 inch line coming to the meter could supply a 1 1/4" line so I looked into it and i guess the pressure to the meter is higher than pressure past the meter. So I am assuming they just adjust/replace the pressure regulator at the meter to get higher pressure?

Ddawg, Isn't the stamped 6-8 wc on my regulator an indication that the regulator should be supplying 6-8 water column?

Last edited by gtzpower; 07-12-2016 at 08:41 AM. Reason: Clarification
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Old 07-12-2016, 08:48 AM   #7
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Re: Gas pipe sizing, plumber says 3/4" is big enough...


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Originally Posted by gtzpower View Post
I wondered about how a 3/4 inch line coming to the meter could supply a 1 1/4" line so I looked into it and i guess the pressure to the meter is higher than pressure past the meter. So I am assuming they just adjust/replace the pressure regulator at the meter to get higher pressure?

Ddawg, Isn't the stamped 6-8 wc on my regulator an indication that the regulator should be supplying 6-8 water column?
I was reading this: https://www.aga.org/how-does-natural...ry-system-work
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Old 07-12-2016, 08:51 AM   #8
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Re: Gas pipe sizing, plumber says 3/4" is big enough...


Quote:
Originally Posted by gtzpower View Post
I wondered about how a 3/4 inch line coming to the meter could supply a 1 1/4" line so I looked into it and i guess the pressure to the meter is higher than pressure past the meter. So I am assuming they just adjust/replace the pressure regulator at the meter to get higher pressure?

Ddawg, Isn't the stamped 6-8 wc on my regulator an indication that the regulator should be supplying 6-8 water column?
Correct...typical residential gas pressure is 7" WC or, about 0.25 PSI. It's done partially for safety.

I've seen pressure for a house as high as 2 PSI. Commercial is going to be in the 7-25 PSI range depending on needs.

I don't know what the gas pressure is on the line feeding your neighborhood, but I'm sure it's in the 10 PSI + range.
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