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Thread: Tankless or 2.5 gal for Undersink Supply of HW for Diskwasher and Sink

  1. #1
    DIY Junior Member JBRoberts38's Avatar
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    Mar 2013
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    Default Tankless or 2.5 gal for Undersink Supply of HW for Diskwasher and Sink

    After an addition, I have to draw almost 2.5 gallons of hot water to get decent temp at kitchen sink. I see where some folks put a small 2.5 gal 120 v heater in what appears to be "in series" on the hot water line. Am I right to understand that I would maybe get 1.5 gal of hot water, then perhaps 10 gallons of warm water (as it mixes) then eventually (maybe) get hot water again?

    I have a 3/4" supplying my dishwasher and kitchen sink (the sink alone is 2.5 gpm). We have 65 lb pressure at faucet, and the lowest temp is 55 degrees (since it is only the crawlspace temp, not the cold tap from county).

    I want to be careful to not drop the flow or pressure across whatever solution I use. I need at least 30 degree rise (even if the water is 80 degrees after the dishwasher fills, the water cools down some before the rinse cycles begin).

    Any idea about sizing for an intant-hot heater? I have seen decent reviews about the Rheem units, and the Park Services uses these around here.

    THANKS!
    JBR

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    If you went with say a 5-gallon unit, you'd probably never see the cold sandwich. But, if you go with a hot water recirculation system, you shouldn't, either. This can end up being much more convenient in the long run, and depending on how you set it up, provide hot water nearly everywhere nearly instantly so you don't waste it when waiting for a shower or filling a tub. Lots of brands out there. There are retrofit units that do not need a return line, but if you can add a return line, you minimize the (usually minor) complaints a retrofit system introduces. You can set the recirc system up as a demand one that only comes on when you ask it to, or put it on a timer, or let it run continuously. If you have access, you could add a dedicated return line, at least for the kitchen sink.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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