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Maximum BTU/hr with 3/4-inch black pipe?

Steve Garson_2
Steve Garson_2 Member Posts: 708
My 115K BTU gas boiler is fed with a 3/4-inch gas pipe. I would like to install an instantaneous gas water heater that will provide 4-GPM, but wonder if the gas pipe will support the two.

Will this work? Or will the load be too large for the pipe?
Steve from Denver, CO


    EBEBRATT-Ed Member Posts: 15,312
    No. Probably not even close. What other gas appliances do you have? What size is the pipe coming off the meter?
    Steve Garson_2
  • ratio
    ratio Member Posts: 3,605
    See attached. (Need to know the length as well.)
  • Jamie Hall
    Jamie Hall Member Posts: 22,912
    You need the input rating of that water heater. It will be at least 130,000 BTUh and possibly as high as 200,000 BTUh.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Steve Garson_2
  • ChrisJ
    ChrisJ Member Posts: 15,443
    With normal gas pressures not even close.

    at 2 PSIG with a pressure regulator at each appliance, probably.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    Steve Garson_2
  • Matt_67
    Matt_67 Member Posts: 284
    Is it natural gas or LP gas?
  • The Steam Whisperer
    The Steam Whisperer Member Posts: 1,214
    Potentially you'll need to upgrade your gas service too. You should also check if these instantaneous units are banned in your area. They are causing problems because they use gas so quickly that the gas network can't keep up if too many of them are installed. They all turn on about the same time everyday in many areas( ie morning showers, etc.)
    To learn more about this professional, click here to visit their ad in Find A Contractor.
    GroundUpSteve Garson_2