# Water Heater Gas Supply Question

Discussion in 'Water Heater Forum, Tanks' started by molo, Mar 3, 2010.

1. ### moloMember

Joined:
Sep 23, 2006
Location:
Cold New York
Hi,
I'm hoping somebody can tell me the required size natural gas supply line for a 120,000 BTU Boiler and a 40,000 BTU Hot water tank. I'm not certain of the supply pressure, but it is less than a pound. This will be black iron pipe.

Thanks for any replies!

2. ### jimboPlumber

Joined:
Aug 31, 2004
Location:
San Diego, CA
Starting AT THE METER ..3/4" pipe would carry 160,000 BTU not over about 20 feet. 1" pipe would carry it 75 feet or so. If you tee off somewhere, you have to factor in the total BTU load on any leg of the pipe run.

4. ### hjModerator & Master PlumberStaff Member

Joined:
Aug 31, 2004
Occupation:
Plumber
Location:
Cave Creek, Arizona
Gas pipe calculations are based on the TOTAL length of the piping to the furthest appliance. Then each section of piping is sized according to the total BTU's of the appliances up to that point. Natural gas is either low pressure, i.e. 6-8 iwc, or medium pressure, 2 psi, and the sizing tables reflect the differences.

5. ### moloMember

Joined:
Sep 23, 2006
Location:
Cold New York
The pressure is approx 7-9 iwc. The water heater (40,000 btu) is right next to the boiler (120,000) and they are about 25 feet from the meter. There is a leg for a gas oven/range that is 15 feet to the side. Here's a rough sketch.

25 feet
meter--------------------------------------------------------------water heater and boiler
gas oven/stove
15 feet to the side