Hi
thinking on getting a gas tankless heater... first does vent pipe get very hot... knowing this will help decide location... also would a 4.3 gpm unit service me in The state of Pa. In a a 2 bath home ?
Thanks
Rick

No, the vent pipe does not get hot because it's inside the combustible air intake pipe.
It depends on how many people will be using hot water at the same time whether that unit will be large enough.

So i could vent this where a child might touch it.... i plan on using the ss vent pipe... running the vent out an existing basement window that will be removed and boxed in ,insulated and covered with appropriate materials

you will have to decide which heater you want to buy and do some research.
find out what their termination fitting looks like and how it functions.
some use a concentric termination some use individual flue-out/ cold-air in pipes.
if you want to use a basement window you will need clearances and you will need to be above ground by whatever height they recommend.
so, you can do it but you will be limited by then manufacturers specifications. these can vary slightly.

Sizing depends on incoming winter water temperatures and household gpm demand.

when i check my incoming water at the closest faucet, i get 40-41 deg F. i would guess it is coming thru the foundation at 38-39.

I'm holding right at 52*.

It depends on the number of people are using hot water.

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