RIMS tube as a tankless water heater for a sink?

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RocketBrewer

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I have a small handwashing sink in my detached garage that has no hot water. Summertime isn't bad, but winter groundwater temp is pretty cold for handwashing. I don't use it often enough to be worth adding a 110v hot water tank and most of the 110v tankless heaters have horrible reviews or require a 30A circuit. I have a 20A GFI outlet already there and running a 220V supply would not be easy or worth the effort and expense. I was thinking about building a simple RIMS tube with a 120v element that would be controlled by a low voltage flow switch and relay board. I know that it wouldn't supply a high flow of hot water, it'd just be nice to have comfortable water in the winter. My biggest concern would be a switch failure that could lead to the element staying on and creating an overpressure in the tube. I've considered using redundant flow switches and could probably incorporate a water heater pressure relief valve without much trouble. I don't know if there are pressure switches available that could cut power if there was a pressure buildup or not. I know there are people much smarter than me lurking here who's opinions and suggestions I'd love to hear (good or bad). Thanks for any input in advance!
 

matt_m

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I had one of the little ~2 gallon tank units installed by the utility sink in the shop at my old place. It just plugged into a standard 15A outlet. It worked out great for 10+ years and was perfect for hand washing, clean a few parts, etc.
 

Bad Bubba

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I would use one with a tank. I bought a Bosch 4 gallon one that uses a 120 outlet. For washing hands and pots and pans it is more than big enough. Not too expensive at $170.
 
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RocketBrewer

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For now, I've decided to try out a 2.5 gallon under sink water heater. I was hoping to go tankless to save electricity, but all the 110v tankless seem to have pretty sketchy reviews. I saw a review on the mini-tank heater that said they tracked the power consumption and it was only costing about $25-$30 a year to run. I can live with that I guess. We'll see how it goes. Thanks for the input!
 

matt_m

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I know the one I had was very well insulated with expanded foam. Actual operating cost will probably be more related to how often you use it than keeping 2.5 gallons of water hot all year. Be sure to flush it once a year, that will help with the efficiency.
 

IslandLizard

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I know the one I had was very well insulated with expanded foam. Actual operating cost will probably be more related to how often you use it than keeping 2.5 gallons of water hot all year. Be sure to flush it once a year, that will help with the efficiency.
One can add more insulation around the tank itself, too.
 
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