Hi,
Just built a new house. 1800 sqft one level. Tankless water heater installed. Same old story...takes 5-8 min to get hot water to the kitchen and the dishwasher will not work properly. I have researched re-circulation systems. However, what I would like to do is add a 6 gallon electric water heater under the sink and connect it to the sink and dishwasher. This is the only problem area in the house. Need input from the Plbg community.

A 6 gallon water heater under the sink may work ok for that, depends on how much hot water you use at the kitchen sink. After about half or 2/3rds of that 6 gallon tank is used the water in the tank will become warm, then cool and it will take several minutes for the water heater to reheat the water in it. For every cup of hot water you use there is a cup of cold water coming into the tank. Some people leave the water running at the sink while they rinse dishes, prepare food, etc. 6 gallons sounds like a lot but you won't get that much since the incoming cold water will start to cool the water in the tank. Smaller water heater tanks are affected more by the intermingling of cold and hot water than larger tanks are. You could connect that 6 gallon WH inlet to the hot water pipe under the sink (instead of the cold water pipe), that way by the time the 6 gallon hot water was gone you'd have hot water from the main household WH. But doing it this way will increase your elec energy usage.

A point of use tankless might work better for kitchen sink and dishwasher. Different models have different minimum flows to activate their heater and different max flows so the water gets heated high enough, so you might take a look at that, but likely the kitchen faucet will use more than enough. And you don't really care if it takes a little longer to fill the dishwasher with hot water if the tankless flow is somewhat lower than normal. Also, you will need to have a large enough elec service under there for the tankless unit (assuming you are not using a gas model), may need to run a new elec cable.

Just so you know, most modern dishwashers have a heating element in the bottom, for drying the dishes at end of cycle if heated drying is selected instead of "energy-saver drying" or non-heated drying. That heating element will also heat the incoming water at beginning of the wash cycle if the water is not hot enough. So the dishwasher should work fine even if it gets cold water to it, although that may not the most efficient way for the DW to get hot water.



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something is wrong if it takes 5 - 8 minutes to get hot water to the kitchen ???
lets say 5 minutes for the sake of argument..
that is 300 seconds. if the water is moving thru the pipe at 1 foot per second x 300 seconds = 300 feet of pipe ??
thats a football fiels long ???
anyway, if you put a 6 gallon electric under you sink and feed it with hot water from the tankless, you should be fine.
since there is no shower involved, i would set the water temperature a little higher.
it's against code but if there are no little children that could get scalded, 135 deg should be adequate.
again, 125 is code so use caution..

When you are standing there waiting on the hot water it probably seems longer than it really is. Maybe the 5-8 minutes is just an estimate.

It's funny how dishwasher manufacturers used to want incoming water at 140* so their products work well so they get no complaints from owners. But the safety rules say hot water shouldn't be higher than 120*. I guess those heating elements in dishwashers get activated a lot in places where the hot water is set at lower temp.



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Thank you for your post. Very helpful. I know for a face that my dishwasher has a heating element so You got me thinking that I may have another issue with the Dishwasher.



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If your water heater is electric there will be no energy savings from a Point of Use for the dishwasher.

The D/W will simply pause while the water is heated (or possibly simply 'spray' longer while the water is internally heated).

Many 'modern D/Wers are, to put it bluntly, pieces of toric ka-ka.

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