Point of Use Hot Water Heater Questions

[Alan Rutherford]

Hot water travels about 60 feet from the tank to our upstairs bathroom and it takes too long to get there. I'm thinking about installing a point-of-use heater with a mini-tank but don't know if it will do what I want. Can I install a 2.5 gallon POU heater in the hot water supply to the bathroom and expect both immediate hot water from the POU heater and a reasonably seamless switch to the hot water from the central HWH when it gets there? There's about a half gallon of water in 60 feet of 3/4-inch pipe. There is not currently a tub or shower in that bathroom (I took out the old clawfoot and have not replaced it) but there will be so I don't want to make the POU heater the only HW source.

Google couldn't find anything here on this subject newer than 2007 so I'm hoping for some more recent experience.

[Malcolm McLeod]

You might consider a small circulator pump? Install under a sink - it pulls water from the hot line and pushes it back into the cold line. Plug it into a timer control, and select the run times for when you want 'instant' hot water.

You'll need convenient access to power, but you'll need that anyway I guess, so the pump and plug might be cheaper and likely more compact that POU heater?

[Alan Rutherford]

I can't believe I'm saying this, but "cheaper" isn't a big consideration here as long as I'm not throwing money away or ending up with a disappointment. The hot water line is well-insulated but the cold is not, so there would be some efficiency lost with the recirculation. And considering the bathroom habits of my age group, prompt hot water would be nice 24 hours a day.

[Bill George]

I can't believe I'm saying this, but "cheaper" isn't a big consideration here as long as I'm not throwing money away or ending up with a disappointment. The hot water line is well-insulated but the cold is not, so there would be some efficiency lost with the recirculation. And considering the bathroom habits of my age group, prompt hot water would be nice 24 hours a day.

Run the circulating pump line back to the water heater via a PEX line you install. Let it run 24 / 7.
A point of use could be a small tank one well insulated plugged in 24/7.

[Edward Weber]

I have a circulator pump installed on top of the water heater. There is a temp sensing valve inder the sink (no power needed for valve).
https://www.homedepot.com/p/Watts-Ho...5800/100426993
There are lots of setting options.
I'm in a rancher and from the heater the master bath is further than your run.
I wouldn't be without it.

[Bill Dufour]

How about a tankless?
The taco pump can have a push button switch at the sink to turn it on and run for two minutes or so.
Bill D

[Brian Elfert]

Why not run hot water from the main water heater into the POU water heater. You should have hot water from the main water heater before the PUO water heater is out of water.

[Alan Rutherford]

Why not run hot water from the main water heater into the POU water heater. You should have hot water from the main water heater before the PUO water heater is out of water.

That's what I'm considering. Trying to find out if it would work as well as I hope it would.

[Bill George]

That's what I'm considering. Trying to find out if it would work as well as I hope it would.

I had assumed that was going to be the case. Why on earth would you try to heat water from the cold water line when there is a hot water line already there?

[Edward Weber]

I think you might be over thinking it.
You have hot water, you just need to get it to where you need it.

A circulator pump keeps hot water on demand at the point where you install the valve. There is no need to wait for water to warm up, no waste, no extra tank, minimal plumbing skills, customizable timer, cheap to run

JMO

[Jerome Stanek]

I have a circulator pump installed on top of the water heater. There is a temp sensing valve inder the sink (no power needed for valve).
https://www.homedepot.com/p/Watts-Ho...5800/100426993
There are lots of setting options.
I'm in a rancher and from the heater the master bath is further than your run.
I wouldn't be without it.

I have the same unit but after having it for a few weeks I installed a return line with a check valve in it. When I first installed it the cold water was warm untill fresh water flowed around.

[Alan Rutherford]

I think you might be over thinking it.
You have hot water, you just need to get it to where you need it.

A circulator pump keeps hot water on demand at the point where you install the valve. There is no need to wait for water to warm up, no waste, no extra tank, minimal plumbing skills, customizable timer, cheap to run

JMO

Maybe I should consider using a recirc pump vs. the POU heater, but I'm not there yet. I'd think the recirculating system could not fail to deliver the hot water. My concerns would be that either I have to run a return line or I return through the cold water line. If I do that, there will be times the cold water is much warmer than expected and that's a problem. If the system includes the kitchen it would also mean sometimes drinking water that has been through the hot water heater, which is not appealing.

The only complaints I can find online about the POU heater are possible short life of the system, which worries me. I can't find any indication of whether you have reasonably constant water temperature as you use the water in the POU tank and it is replaced first by cooler water from the hot water pipes and then hotter water fresh from the central HWH.

[Bill George]

The POU heater is going to require a 15 amp circuit just for the heater, most have 1400-1500 watt elements.

[Paul F Franklin]

So if you feed the POU tank from the hot water line, where is the cold water that's in the line going to go? If you only need a little hot water, it will be fine, but once the POU tank is empty, you'll have cold water again until the hot water arrives from the main tank, because the POU heater won't heat the water quickly. Might not be an issue for a tub, but not what you want for a shower.

The recirc setups will do what you want, but they have downsides too. If you don't run a return line, you'll have hot/warmish water from the cold faucet for a while when first turned on. And those systems do waste energy because you will end up heating more water than you would otherwise. This can be minimized by using a pushbutton to activate them rather than letting them run 24/7 or putting them on a timer. But then you have to wait a bit after pushing the button before the hot water arrives. But at least the water isn't just running down the drain while you are waiting. And face it, most time you have a minute or two in the lav before you are ready to shower or wash your hands.

[Malcolm McLeod]

I have a circulator pump installed on top of the water heater. There is a temp sensing valve inder the sink (no power needed for valve).
https://www.homedepot.com/p/Watts-Ho...5800/100426993
There are lots of setting options.
I'm in a rancher and from the heater the master bath is further than your run.
I wouldn't be without it.

Interesting rig. As I read it, seems pump can run some or all the time, but crossover valve only opens when hot water supply at install point (sink?) is <95F. That should reduce heat lost in the cold line (if used as return).

I've had (or have now) 2 systems; both just pumped on timer, but Mr. Rutherford's water usage patterns may require another solution.