Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.

If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
Need to contact us? Visit https://heatinghelp.com/contact-us/.

How many tankless gas water heater will plumber need.

bob eckbob eck Posts: 844Member
Please just the answer to my questions. Please no video of the bear telling me I am a idiot for wanting to sell or install tankless gas water heaters. There is a market for tankless gas water heaters and tank type gas water heaters

House will have seven (7) showers with 2.5 GPM shower heads. No tubs. Kitchen sink, 7 lava faucets, dishwasher, washing machine.

Well water 50 F degrees incoming 70 F temp rise to 120 F degrees.

I told the contractor to check how many GPM the well pump will produce.

How many 199,000 TGWH will be needed?

I say reduce all shower heads to 1.5 GPM and I would install two (2) 199,000 BTU TGWH and I should get about 9.5 GPM max at a 70 F degree rise.



Comments

  • Jamie HallJamie Hall Posts: 10,177Member
    Yep. If you use 1.5 gpm shower heads, that should work. Are you planning on hooking these puppies up in parallel? If so, control may be an issue. Or you could split the system, making sure neither one is overloaded.

    if they insist on 2.5 gpm showers, they're going to need 3 units rather than 2.

    That, however, is a lot of BTUs. make sure the gas lines can handle it!
    Jamie



    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.



    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • GordyGordy Posts: 9,263Member
    398k to bath, wash dishes, and do laundry. That’s barely enough.......

    Is there a chance everything will go at once?

  • hot_rodhot_rod Posts: 11,228Member
    that is the big question, how many load concurrently?

    1.5 gallons shower heads were mandated by the federal water act over 20 years ago
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Jamie HallJamie Hall Posts: 10,177Member
    "that is the big question, how many load concurrently?" The old National Plumbing Code had a table for that -- which was pretty good. I have no idea where my copy has gotten to...
    Jamie



    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.



    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • GordyGordy Posts: 9,263Member
    9.5 gpm covers only 7 showers with 1.5gpm heads......only :)

  • JohnNYJohnNY Posts: 2,201Member
    Are you buffering these with electric tanks? Add those BTUs too.
    For installations, troubleshooting, and private consulting services, find John "JohnNY" Cataneo here at :
    "72°F Mechanical, LLC"
    Or email John at [email protected]
    John is a professional Master Plumber, licensed by The Department of Buildings of The City of New York, and works extensively in NYC while consulting for clients in and out of state.
  • mikeg2015mikeg2015 Posts: 701Member
    Use a recirc pump and electric WH as buffer tank and i unit will be plenty with a 75 gallon buffer. Set to 140F on tank and use mixing valve.

    Recirc in large home should be code required. Will save 5 gallons each shower from a cold start and drop your overall demand by a lot.

    Might use a 2nd WH just to be safe for max flow rates. They will cascade. Only 1 needs Circ pump,


    AS a counterpoint, with well water, I’d surge you to use a 100 gallon 199k commercial condensing water heater like a AO Smith cyclone and be done with it. A little more equipment cost, but Less issues and can still use a recirculating pump. Can add an electric WH for extra buffer or mixing valve and store at 160-180F.
  • gennadygennady Posts: 726Member
    edited February 13
    the question is what is probable maximum demand? what are the chances all these fixtures will work at the same time?
    Gennady Tsakh



    Absolute Mechanical Co. Inc.

    www.AbsoluteMechanicalCoInc.com
Sign In or Register to comment.

Welcome

It looks like you're new here. If you want to get involved, click one of these buttons!