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Afraid my plumber is making a mistake

Posted by elinpedersen (My Page) on
Fri, Apr 19, 13 at 18:20

I am looking for advice. Is my plumber about to make a really big mistake or is it just me who doesn't know how to read the UPC table?

The gas meter has these measures according to PG&E: capacity is 0.25264 psig, 0-425 CFH incoming pipe is 3/4".

A previous plumbing job ran a 1" pipe from this meter to an existing furnace and water heater (outlets A and B below).

Now we have these three outlets. The selection of on demand water heater (outlet C, 200kBTU) was made with the plumber.

Outlet A: YP9C100C20MP11 Furnace 100,000 BTU
Section 2: 5' of 3/4"
Section 3: 1' of 3/4" (or 1/2"?)
Section 1: 50' of 1"

Outlet B: Water heater tank - 40,000 BTU,
Section 2: 5' of 3/4"
Section 4: 1' of 3/4" (or 1/2"?)
Section 1: 50' of 1"

Outlet C: Noritz water heater, 200,000 BTU,
Section 5: 80' of 3/4"
Section 1: 50' of 1"

Outlet C/Section 5 is a new addition, and the plumber wants to branch off a 3/4" from the section 1-2 connection. But according to the UPC charts, 3/4" can at most deliver 118 kBTU over 80'.

Looking at the UPC table it looks to me like I would need a 1-1/4" from meter (section 1) and a 1" for section 5. And most likely I would need a new meter as well.

What really troubles me is that the plumber is evasive when I ask directly about this. And he even says that the 3/4" line will have to work because the meter cannot feed anything larger. But I am reluctant to add an expensive water heater only to starve it - and possible damage it - because it not getting enough gas.

Please help me clarify this: is my plumber right, and if so, how is the calculation done? Or do I need to find myself a new plumber?


Follow-Up Postings:

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RE: Afraid my plumber is making a mistake

Call your gas company and ask them what you need. They will have the correct answer for you.

This post was edited by aliceinwonderland_id on Fri, Apr 19, 13 at 18:54


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RE: Afraid my plumber is making a mistake

@aliceinwonderland_id: I wish it was that easy ;-( PG&E is not providing that level of service. They can offer a meter upgrade, but do I need that? and would that solve my problems? Asked these questions they refer to a licensed plumber... who is the fellow I don't think I can trust.

I am hoping that someone on the forum is sufficiently experienced with meter sizes and gas line sizing to quickly review my installation spec for feasibility. Please !


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RE: Afraid my plumber is making a mistake

"The gas meter has these measures according to PG&E: capacity is 0.25264 psig, 0-425 CFH incoming pipe is 3/4". "
Possible confusion as these numbers are presented. The incoming 3/4 pipe is at pressures of at least 10 PSI and more likely at 100 PSI-- the incoming pipe has plenty of capacity for any meter you might need. The 0.25264 psig is the pressure in the gas piping inside your premises and the 425 cfh is the stated maximum flow rate for that meter. What is the largest pipe that the outlet of the meter will accept?

Try this chart. Not as good as the first one but this link should work.

Here is a link that might be useful: Chart

This post was edited by bus_driver on Sun, Apr 21, 13 at 8:40


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RE: Afraid my plumber is making a mistake

@bus_driver: Sorry, but I cannot get to the chart. Tried both Chrome and Safari. The redirection fails with an "unhandled exception" (a nullReference).

And thanks for clarifying the info from PG&E about my meter.

I believe the largest pipe is a 1" - but I am basing this entirely on what the plumber said.


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RE: Afraid my plumber is making a mistake

Here is the chart.

Tried a few times, GW still messed up the format by removing spaces between columns of each row. Hope it is readable.

Pipe Sizing Chart for Natural Gas

The chart below is based on gas pressure in the range 0-0.5 psi, specific gravity of 0.6, and pressure loss of 0.5” WC. Numbers are for straight schedule 40 pipe; fittings further reduce capacity. For example, in 1” size, an elbow is equivalent to about 2.6 feet of pipe, and a tee is equivalent to about 5.2 feet of pipe.

Maximum capacity of pipe in cubic feet/hr of natural gas
(Multiply values by 1000 to get nominal Btu/hr capacity.)

Length of pipe(ft) Iron pipe size

feet 3/4” 1” 1-1/4” 1-1/2” 2”
10 360 680 1400 2100 3950
20 250 465 950 1460 2750
30 200 375 770 1180 2200
40 170 320 660 990 1900
50 151 285 580 900 1680
60 138 260 530 810 1520
70 125 240 490 750 1400
80 118 220 460 690 1300
90 110 205 430 650 1220
100 103 195 400 620 1150
150 84 160 325 500 950
200 72 135 280 430 800


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