How many tankless gas water heater will plumber need.

bob eck

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.

Jamie Hall

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!

Gordy

398k to bath, wash dishes, and do laundry. That’s barely enough.......

Is there a chance everything will go at once?

hot_rod

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

Jamie Hall

"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...

Gordy

9.5 gpm covers only 7 showers with 1.5gpm heads......only

JohnNY

Are you buffering these with electric tanks? Add those BTUs too.

mikeg2015

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.

gennady

the question is what is probable maximum demand? what are the chances all these fixtures will work at the same time?