Recommendation for small point-of-use under-sink heater? Goal is to save water.

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KarenTheBold

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In the California drought, I still want warm/hot water in the bathroom sink, without running gallons of non-hot water down the drain just to get a small amount of water for handwashing. (A new whole-house heat-pump water heater is about 10 feet away, but I can't stand waiting and watching cold water going down the drain, so I've always been washing my hands in cold water.)
For the bathroom application I'm thinking one of the smallest tankless POU water heaters, but would get a small tank model (1.5 gal) if that's a better choice. Existing 120v outlet.
I welcome recommendations re specific brands, tank or tankless.
 

wwhitney

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How about an under sink on-demand recirculation pump that pushes water from the hot line back into the cold water line until the water in the hot line gets hot? You just push a button when you want it to run. That's the equivalent of running the water, without letting it go down the drain.

Cheers, Wayne
 

KarenTheBold

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How about an under sink on-demand recirculation pump that pushes water from the hot line back into the cold water line until the water in the hot line gets hot? You just push a button when you want it to run. That's the equivalent of running the water, without letting it go down the drain.

Cheers, Wayne
Thanks, Wayne, but I'm not patient enough to push buttons or wait for hot water to get to the sink directly or via recirculation. Therefore all the COVID advice to wash hands frequently means I'm washing quickly in cold water. I'm willing to put money behind a solution that means I can have warm water for handwashing at last. (I'm just across the Bay from you, in Mountain View. The new toilet in that bathroom is 1.0 gallons!)
 

wwhitney

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Well, there are also motion sensor options for controlling the pump. Since you say the water heater is so close, depending on the bathroom layout, I bet the pump could be done by the time you reach the sink.

As to the original question, there are a number of 2.5 gallon tanks that would do what you want. I once had an InSinkerator W-152 for something similar, and I was happy with it, but it's been discontinued. So I don't have a specific recommendation, sorry.

Cheers, Wayne
 

WorthFlorida

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Here is another option. Chronomite has dozens of different models depending on power and temp rise. Some are 120v and others 240v. No storage tank and all controlled by water flow sensor and temp rise wanted. Some are adjustable for temp others are fixed temp rise, usually to 105 degrees. It draws no power when not in use. I've installed 2 gallon water heaters and they take up a lot of space under the sink. The main issue is power if you can run another circuit.
It can be connected to the hot water line, therefore, it will only be on until the cool water in the line is depleted. When the hot water temp gets above the setting or 105º, it switches off.

 
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KarenTheBold

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Here is another option. Chronomite has dozens of different models depending on power and temp rise. Some are 120v and others 240v. No storage tank and all controlled by water flow sensor and temp rise wanted. Some are adjustable for temp others are fixed temp rise, usually to 105 degrees. It draws no power when not in use. I've installed 2 gallon water heaters and they take up a lot of space under the sink. The main issue is power if you can run another circuit.
It can be connected to the hot water line, therefore, it will only be on until the cool water in the line is depleted. When the hot water temp gets above the setting or 105º, it switches off.

WorthFlorida, thanks for bringing this brand to my attention. This option looks like a winner. Tankless, 120v, cord to plug in.
 

wwhitney

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Wayne, the description shows the small 120v Chronomite tankless heater with a plug and 3' cord. Here's the description: https://www.amazon.com/Chronomite-120VAC-Undersink-Electric-Tankless/dp/B08F5CX5RS
The model number referenced above is Chronomite Labs SR-20L/120. https://www.chronomite.com/instant-flow-tankless-water-heater-sr shows SR-20L/120 rated at 20A and 120V, unsurprisingly given the model number.

Such a load would not be permitted on an electrical branch circuit that supplies more than one receptacle, per NEC 210.23(A)(2). It would be OK to run a new dedicated 20A circuit to a single NEMA 5-20 receptacle, and then the product can be cord and plug connected to that receptacle.


The same would apply to their 15A/120V product, except then a standard NEMA 5-15 receptacle and 15A branch circuit could be used.

Cheers, Wayne
 

WorthFlorida

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What I like about Chronomite is even at 120v units, only takes .35 gallons a minute flow rate to turn on. There is a model SR 15/120. (15a/120v). They do have many other models.
 
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