[Robert Gift]

If I must spend $400 for a new 50 gallon water heater, should I put that $400 towards a $1,000 tankless water heater at Home Depot?
Plus stainless steel air intake/exhaust pipe. (Why musthat pipe be so expen$ive?)
Does anyone make a water heater which closes the flue so heat is not lost by convection 24/7?

At bathroom sinks, with the little hot water needed to wash hands, etc. an electric water heater under each sink would provide all that is needed, instantly. One sink especially takes a long time for the hot water to arrive. (I could run a pipe though the wall and bring its hot water from another sink's heater.)

The only time we need a larger supply of hot water on the second floor is for a shower.

Thank you.

Robert

[CHayn]

Tankless water heaters are great in the correct applications. You need to make sure your gas pipe is sized correctly to provide enough gas for the BTUs a tankless uses. There are even cases where the gas meter needs to be updated to provide enough gas. Minimum 1" main gas line in the house.
It is easiest and most economical to mount on an outside wall because of the cost of stainless venting. You may need to move your water lines to accommodate that.
Your tankless will heat your water to the temp desired. If you are using multiple fixtures it will slow the water down to reach that temp thus giving you lower volume of hot water at each fixture.
A tankless requires annual servicing. They need to be delimed annually.
They DO NOT provide instant hot water. You will wait just as long or longer than a tank type heater for hot water to your fixtures.

[Robert Gift]

Yes. If I can vent it horizontally, it would not be so bad.
I'd have to reroute the hot water line.

I was considering installing an instant hot water pump but that would not work with a tankless water heater.

[Widdershins]

Yes. If I can vent it horizontally, it would not be so bad.
I'd have to reroute the hot water line.

I was considering installing an instant hot water pump but that would not work with a tankless water heater.

The Takagi TH-2 is compatible with the Uponor D'MAND circulating pump

[CHayn]

You could also search Navien. I believe their heaters can have a recirc line. Check out the flow rates though. At 90 degree rise the flow rates are not very good. One fixture at a time would be okay, but not multiples. That goes for all tankless heaters.

[Robert Gift]

This all makes my below sink 2 gallon electric water heater seem better.

[Widdershins]

This all makes my below sink 2 gallon electric water heater seem better.

Or, for about $250.00 you could install a single Laing Autocirc circulating pump under the sink furthest from the HW Tank and circ the entire house.

[Robert Gift]

Or, for about $250.00 you could install a single ...circulating pump under the sink furthest from the HW Tank and circ the entire house.

Thank you. These are nice, smart systems.

We have two problems:
-Our kitchen and laundryroom and bathroom sinks are all separate branches.
-Circulating hot water creates heat losses which would cause water heater to operate more.

Our uses are all over the place, not at usual times around which I could turn off the circulation pump. (It could be off from 11 p.m. to 5 a.m.)
Seems that if I installed a 2-gallon electric water heater beneath each sink, and set the temperature at 110 F. one could turn on just the hot water and instantly get the temperature they want. No need to adjust by mixing with cold water.
Electric water heating is 100% efficient and if well insulated the tank should hold the heat well.

[Widdershins]

Thank you. These are nice, smart systems.

We have two problems:
-Our kitchen and laundryroom and bathroom sinks are all separate branches.

How long are the branches?

Are they insulated?

If the branches are 25' or less (even with a vertical rise of 8 to 10 feet) and the branches are insulated then the wait time at each outlet as it purges the ambient temperature water already in the branch is going to be negligible.

-Circulating hot water creates heat losses which would cause water heater to operate more.

Assuming the lines are in fact well insulated, exactly where is this heat loss taking place?

Seriously.

If the piping is correctly insulated and the joist/stud bays the piping passes through are correctly insulated, then there should be no heat loss whatsoever, assuming the house is lived in and the fixtures are purged on a daily basis, of course.

Our uses are all over the place, not at usual times around which I could turn off the circulation pump. (It could be off from 11 p.m. to 5 a.m.)
Seems that if I installed a 2-gallon electric water heater beneath each sink, and set the temperature at 110 F. one could turn on just the hot water and instantly get the temperature they want. No need to adjust by mixing with cold water.
Electric water heating is 100% efficient and if well insulated the tank should hold the heat well.

The system you describe would likely be more efficient than trying to retrofit a circulating pump/return line into your existing water delivery system -- No doubt about it.

OTOH, a 2 gallon H/W tank at each sink location is going to require a dedicated 110 GFCI protected power source -- No, you will not be allowed to tap into the existing 110 sources wired into each location -- Assuming you're going to be doing this to code, of course. The amperage draw for these units is going to be much greater than that of the wiring already in place.

You're also going to be losing some Prime storage space, of course.

My opinion -- You're overthinking this.

Still.. .

If you're going to go through with this -- Spend the money and buy decent point of use tanks.

I'm partial to the Bosch Ariston tanks, by the way.

[Milo Dolezal]

You can purchase Tankless hot water heater for Exterior installation and put it into enclosure. Here you would have no issue with vent (vents directly out of the heater). You would just have to re-route your h/c water pipes and gas.

Tankless heaters are way to go. Presently, you can get up to $1,500 tax credit for installing one. Our company installs Tankless heaters since they arrived in the US. It is my opinion that Rinnai tankless hot water heaters are the best units on market.

Booster / point-of-use hot water heater under you sink is a popular solution to slow hot water delivery to kitchen sink. However, suggested 2gln heater is too small for you. You will need 4gln to 6 gln Bradford White unit or 4gln Aristar from Home Depot.

Please, let us know what you decided to do. Best of luck. Milo

[Robert Gift]

I presume the vent has to exit away from any door or openable window.
That limits it to the west side of the house which is far from all the plumbing which is on the east side.
When they say "tax credit", does that mean I could get all the costs back?
Thanks for you advice.

[CHayn]

You get up to 1500 dollars back. Up to 30% of your cost of installing the heater. The heater has to be a minimum of 90% efficient. And that tax credit is a max of 1500. If you already claimed for windows, or doors, appliances, etc and already got 1450 back you will get a total of 50.
You do understand that a tankless heater does not give you instant hot water at your faucets, right? You will actually wait longer (not much) for hot water. The only ways to avoid that wait is to install the recirc lines or the point of use heaters as you have mentioned. If you pipe the supply side of the point of use heaters from the hot side to your current heater a small heater should give you enough water to last until the truly hot water arrives from your current heater.

[Robert Gift]

you get up to 1500 dollars back. up to 30% of your cost of installing the heater. the heater has to be a minimum of 90% efficient. and that tax credit is a max of 1500. If you already claimed for windows, or doors, appliances, etc and already got 1450 back you will get a total of 50.
You do understand that a tankless heater does not give you instant hot water at your faucets, right? You will actually wait longer (not much) for hot water. the only ways to avoid that wait is to install the recirc lines or the point of use heaters as you have mentioned. If you pipe the supply side of the point of use heaters from the hot side to your current heater a small heater should give you enough water to last until the truly hot water arrives from your current heater.

Thank you, CHayn.
So if I do the installation entirely myself, I would get back about $300 from the $1000 heater?
Can't afford the $700 now.
Yes, slightly longer for the water to quickly heat and then travel to the faucet.
A circulation pump causing the water to be heated and delivered to the faucets would be very expensive - starting the heater frequently and losing heat radiated from the pipes.

Seems best would be to heat the water beneath the sink. We do not use much to wash hands and brush teeth.
A 4-gallon heater set on very warm would provide all the water needed just from the hot side - without needing to mix hot and cold for the desired temperature.

If you wish, please see my other idea about tapping 200 F. water from a hot water dispenser to mix with the cool water to the provide instant hot water at the kitchen sink faucet.