Gas pipe sizing

[skatona]

PG&E tells me to ask a plumber, so...

I have added some gas load and recalculated my new gas supply requirements using an example I found online, and the standard table for distance vs CFH to check pipe sizes. My meter will supply enough in total, so no problem there. Per the calcs, because of a 35 foot initial run to the first load, I know I need to increase my supply line to 1" from the existing 3/4", then I can size back down to 3/4 once the first load is out of the picture.

The table shows that a 3/4" pipe can supply 363 CFH at 10 feet from the meter (the meter can only supply 275; my total demand is 260).

The question: For convenience I'd like to tap into the existing 3/4" line about 5 feet from the meter, upsize to 1", continue the next 30 feet, then after the first load reduce back to 3/4. Can I start my 1" line 5 feet from the meter?

 

[ToolsRMe]

I am not a professional plumber so take this with a brick of salt.

The answer I have is: no.

The problem you have is with the proverbial bottleneck. It doesn't matter how big the bottle is: if the bottleneck is small then that's all the volume you're going to get through the bottleneck.

In your case the bottleneck is five feet long.

Basically, you don't gain anything (well, very little) by putting in one-inch pipe after a three-quarter inch bottleneck.

Again, please take this with a brick of salt.

I'd be very interested in knowing how close I came to the right answer.

 

[Sponsor]

 

[hj]

gas size

In the first place you seem to be reading the gas chart incorrectly. You compute the TOTAL length of the gas line from the meter to the furthest appliance, and then make all size calculations from the column that is equal to, or longer than, that measurement. You can connect to the 3/4" opening, but you should increase to the proper size immediately.

 

[hj]

gas size

In the first place you are using the gas table incorrectly. You measure from the meter to the furthest appliance and use the column with that measurement, or the next longer one, for all calculations as to size according to the gas load on each section.