Under Sink Water Heater

[LittleBittyBigJohn]

One of the many irons in my fire right now is finishing up the inside of my shop after my house build a couple of years ago. I changed gears a little bit and have decided to just put a toilet and sink in, instead of a full bath. Now I don't really have any need for a full size water heater any more. Do any of you have experience with the small point-of-use tankless water heaters that go under the sink? I hope a 110v unit would be sufficient for just a sink, but I don't have any experience with them at all.

 

[Topzide]

I have a Chromite 208 volt unit under my kitchen sink. I'm on well and it delivers 120° hot water. I don't think that you'll get go performance from a 110 unit. Have you looked at the propane units? That might be a better choice if you don't want a double pole breaker. The 208 volt unit gives better heating than the 240 unit. Been in service since '98.

 

[Grendahl]

I have a 120V point of use water heater on my shop sink. I think it holds 2 gallons of water. It works fine for low usage applications like a hand-washing sink. There is plenty of time for the heater to catch up again between uses.

 

[nybirdman]

If you have "hard water" it could be a problem(not lasting).

 

[bdhsfz6]

Is your shop attached to the house? If so, have you considered tapping the house water system?

That's what I did with my attached shop. It's a long run so I installed hot, cold and return piping so I could use a hot water recirculating pump. I turn it on when I'm in the shop so I have instant hot water with no waste.

 

[LittleBittyBigJohn]

Is your shop attached to the house? If so, have you considered tapping the house water system?

That's what I did with my attached shop. It's a long run so I installed hot, cold and return piping so I could use a hot water recirculating pump. I turn it on when I'm in the shop so I have instant hot water with no waste.

It's not attached to the house.

 

[GrandpaSmurf825]

This would be your best bet. Providing you have the electrical capacity for a 30 amp 120 volt breaker. You only heat water when you need it. It will provide more than enough to do your hand washing and whatever else you need. Constant flow of .5 gpm at 120 degrees which is plenty warm.

https://www.homedepot.com/p/ATMOR-3-5kW-120V-0-5-GPM-Point-of-Use-1-Sink-Electric-Tankless-Water-Heater-with-Pressure-Relief-Device-2-Pack-AT-35WH-HD2PK/315654515#see-more-details

 

[oldnslo]

I have a tankless point of use in our 1/2 bath and big problem is if you run hot water, shut faucet off for a short period of time and then hot water back on ALL of the heat from heating element went into that water and it comes out scalding hot. Very concerning if have younger children or you forget to tell someone about that feature. Other than that it has been working fine for several years.

 

[34Willys]

These units don't work 'as advertised'. Here is the fine print -

• Durable, point-of-use hot water solution ideal for a single sink application in areas with at least 57 degrees F ground water temperature.
• Manufacture states do not use with water less than 57'F.
  

Maybe in South Florida you get tap water that warm.
My well water comes into the house at 40'F, and there's not enough BTUs in that little unit to heat it to anywhere near 120'F. And, to get it warm, you'd have to choke down the flow where you wouldn't have enough GPM to wash or rinse much.
I would mount an outdoor propane unit. We have one for an out build that supplies two full baths with showers at the same time.
They make smaller units, and electrical sized properly.

Patrick

 

[ultrarunner]

I will take a picture tomorrow if a small under counter unit installed 11 years ago.

I was skeptical but so far so good.

I also have same at the cabin but twice in 45 years freeze damage got it…

Might be a consideration if freezing temps occur in the shop?

 

[GrandpaSmurf825]

These units don't work 'as advertised'. Here is the fine print -

• Durable, point-of-use hot water solution ideal for a single sink application in areas with at least 57 degrees F ground water temperature.
• Manufacture states do not use with water less than 57'F.View attachment 5017650

Maybe in South Florida you get tap water that warm.
My well water comes into the house at 40'F, and there's not enough BTUs in that little unit to heat it to anywhere near 120'F. And, to get it warm, you'd have to choke down the flow where you wouldn't have enough GPM to wash or rinse much.
I would mount an outdoor propane unit. We have one for an out build that supplies two full baths with showers at the same time.
They make smaller units, and electrical sized properly.

Patrick

According to this it will be fine. This is one of many water temperature maps that shows it's above that. Good point though. It appears to only be that brand or maybe that model.

 

[GrandpaSmurf825]

I have a tankless point of use in our 1/2 bath and big problem is if you run hot water, shut faucet off for a short period of time and then hot water back on ALL of the heat from heating element went into that water and it comes out scalding hot. Very concerning if have younger children or you forget to tell someone about that feature. Other than that it has been working fine for several years.

That wouldn't be good. Even if it's not a child 120 is getting pretty hot. I wonder if all of the point of use models have that characteristic?

 

[bumperm]

You've gotten good advice. I'm using a 120V under sink heater for a deep sink in my shop. Works fine for washing hands and the like. I tend not to heat the shop to more than 40 - 50 degrees to save on propane, so have a little electric in-wall heater near the toilet with a timer switch for those sit-down occasions . . . mustn't freeze ones (censored) off.

 

[not2old]

I plan on installing what my brother did and is happy with. A 5 gal 220V tank controlled by a thirty minute timer. He turns it on when going out to the shop and it keeps the water warm enough all dayt. 220V heats it up pretty fast.

 

[LittleBittyBigJohn]

I will take a picture tomorrow if a small under counter unit installed 11 years ago.

I was skeptical but so far so good.

I also have same at the cabin but twice in 45 years freeze damage got it…

Might be a consideration if freezing temps occur in the shop?

Yes please do that. I have been seeing less than stelar reviews saying about the same as everyone above has been saying on the tankless being a bit underpowered.

My plan in the freezing temps is to blow the water out of the lines. I am plumbing in a tee with ball valves on all sides. That will allow me to cut off the water flow to the shop and pressurize the system with air. Then I can open each valve until just air comes out and put some RV antifreeze in the toilet. Hopefully that will keep me from having damage from freezing. I'm also using PEX it's not as prone to bursting as copper.

According to this it will be fine. This is one of many water temperature maps that shows it's above that. Good point though. It appears to only be that brand or maybe that model.


View attachment 5017652

For summer time you are correct. But I'm on city water and that is stored in water towers high in the air, so our water in the winter is cold-cold.


These units aren't stupid expensive. I'll probably pick one of the better ones I see from somewhere I can return it if it sucks. I'm planning on wiring a 20a 110v plug, and pulling a wire for 30A 220V just in case, under or near the sink. My 220V air compressor is close enough that I'll just piggy back off of it if I need the 220V. No more than I will use the hot water I can just make sure the compressor is not running when I use it. 10/2 Romex is expensive and my panel is about 50' from my sink.

 

[WM75Guy]

We put in a sink in our stained glass shop several years ago, to wash glass pieces and our hands. I put in a conventional electric 6-gallon hot water heater. It works well for us.

Freezing is an issue for us as well. I hung a 50,000 BTU electric heater near it to keep the pipes from freezing and to keep the glass warm. It doesn't do the job and is very expensive to operate. I am installing a 4-ton HVAC system in the very near future, as soon as the electrician gets the wiring installed.

 

[HawkinsHollow]

Following! I plan on putting a sink and point of use heater in my shop as well. Interested to hear what y'all have to say.

 

[oldnslo]

That wouldn't be good. Even if it's not a child 120 is getting pretty hot. I wonder if all of the point of use models have that characteristic?

I believe most point of use low volume tankless heaters do not have a thermostat or water mixing valve so the potential for scalding with on off use is there. On mine hot water temperature is regulated by water flow.

 

[Topzide]

This is the little unit I have. 20 amp double pole breaker. Using a bar sink faucet with 0.5 gpm aerator. Has been in service over 20 years!

 

[ultrarunner]

I will take a picture tomorrow if a small under counter unit installed 11 years ago.

I was skeptical but so far so good.

I also have same at the cabin but twice in 45 years freeze damage got it…

Might be a consideration if freezing temps occur in the shop?