You all will first note that I did NOT say hot water heater.

I am thinking that a tankless heater would be ideal. Located at the gas main pressure regulator outside, I would have to run maybe three feet of expensive gas pipe. Also at this point we find a cold water supply at the outside faucet. So, it would seem, that we could bring that water line to the cold water heater.

Now, for the specific question. If the kitchen sink, which does need hot water, is within ten feet of the outdoor tankless heater, AND, if the kitchen sink is plumbed to the present garage tank heater, couldn't I put the new hot water supply line first to the kitchen sink, and simply cap the hot water lines in the garage? Wouldn't the kitchen sink essentially back feed the entire home?

This way, I don't have much plumbing line to run, gas line to run, and electricity to run.

I also gain space in the garage to put a gun cabinet. Not that I have any guns.

This message has been edited. Last edited by: 4MUL8R,

My 1.5 year old home was constructed with a Rinnai gas tankless water heater built between the studs in my garage. Outdoors, there is a panel with vents on it and indoors there is a digital temperature display and temperature controls. It's real close to my gas meter.

I think it's a recess box kit combined with a regular tankless water heater.

You can feed the whole house from the new line but your new heater needs 3/4" feed and outlet to get proper volume to the whole house. Follow the kitchen line back to a 3/4 source.

^^^ There's your answer.

I put one in for my Sister a couple years ago. Consider the optional automatic freeze protection kit if you live in a climate where it freezes. It drains the tank and outdoor pipes in the event of a power failure.

If you live in an area where it gets really cold, do you have to protect the water lines from freezing, both incoming supply and the water line feeding into the house? Say overnight when their is no demand?
The house we live in in the Black Hills has a Rianni, but it is indoors, and a small house, < 1000s.f. so not a problem. But when it is below zero all night, and maybe a high of 6° or so during the day? The water lines here are buried 6' or greater. Rock almost all the way!
Oops looks like the previous post answered my question!

Is your water heater currently mounted on the exterior wall of the garage?

If so, generally they mount the Rinnea outdoor unit directly on the exterior wall outside of where the existing heater is, then simply punch 2 small holes (or 1) in the wall and run the supply and discharge plumbing from the existing heater through the wall to the Rinnae. Then run the gas line to it and off you go. If your water heater is on the inside of the exterior wall and you can mount the Rinnau outside on the exterior wall, that's the easiest method in most cases.

I'm going to be condescending...

You need to hire a plumber or at least find someone who knows about plumbing...

And by the way... gas piping is not expensive.

As a builder here in VA I would not mount a tankless water heater outside. It gets too cold here...

Reading the requirements and cautions you all have kindly provided, I will NOT be installing a tankless outdoor. I'll be needing a SF-quality plumber to put in the SF-quality 50 gallon gas heater in the garage. Richmond VA...wonder if there are any SF-quality plumbers?

Go here and enter your zip code.
http://www.bradfordwhite.com/rep_locator

Then call the distributor and ask them for the name of the dealers who do quality work.