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Thread: Water Heater Gas Supply Question

  1. #1
    DIY Senior Member molo's Avatar
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    Default Water Heater Gas Supply Question

    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!
    "Any American who is prepared to run for President should automatically, by definition, be disqualified from ever doing so."
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  2. #2
    Plumber jimbo's Avatar
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    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.

  3. #3
    Moderator & Master Plumber hj's Avatar
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    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.

  4. #4
    DIY Senior Member molo's Avatar
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    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
    "Any American who is prepared to run for President should automatically, by definition, be disqualified from ever doing so."
    Gore Vidal.

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