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Increase ambient winter water temp with holding tank

I have an on demand hot water heater (slant/fin combicat) which works well other than when filling the soaking tub when the water flow is high. We just have to decrease the flow and it makes hot water, but it take a while to fill the tub.

I'm wondering if a storage tank in the basement would would claim some heat from the temp of the basement and increase the ambient temp much, so that the winter cold water isn't so cold when it hits the hot water heater?

Is this a possibility or a far fetched idea I have come up with?


  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    It will work but....

    That heat that is in your basement isn't free. You paid for it, and it just escaped and is hanging out in that spot.

    The problem with your idea is that the tank will condense, and the condensate will rust the exterior of the bare naked tank.

    The issues you bring up regarding filling a large fixed volume tub are one of the negative detractors of tankless heating that most consumers are not aware of. I have my wife trained to start filling her tub about 20 minutes before she's going to use it at a slow flow rate so that the tub is nice and HOT when she hops in.

    It's all in the details :-)

    If you can accomodate the condensation, then it will lessen the wait time for a full tub, but be prepared for the moisture the bare tank will generate.

    You could consider installing a hybrid air source heat pump that would boost the incoming water temperatures, but again, that heat that you will be recovering has already been paid for once....


    There was an error rendering this rich post.

  • Charlie from wmass
    Charlie from wmass Member Posts: 4,322
    I have seen

    copper tanks often used for this. If you saw the innards of these tanks after a few years you would not want to bath in the water. Slow the flow or add a small booster heater if you are in a hurry to relax in your tub. You could pipe a plate heat exchanger in series with the existing heat exchanger to kick in if demand is not being met. This would run as a separate zone and would need to be controlled and wired properly. This is also dependent on the boiler having enough power to heat both heat exchangers at the same time.
    Cost is what you spend , value is what you get.

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  • bill_105
    bill_105 Member Posts: 429
    Hot water??

    People seem to learn how there hot water behaves rather quickly. Now, enough of that highly technical mumbo jumbo.

    This wife training thing is fascinating, though. Is there a book out there like, "Wife training for dummies" ?  I'll tell you I can use it!! All the best !!
  • spacoli
    spacoli Member Posts: 61

    Thanks for all your input and ideas.

    We don't use the tub daily, only once in a while.  I just think it's just something we are going to have to deal with and wait for the tub to fill.

    Other than the slight lag time to wait for the hot water, the Combicat work great.
  • bob eck
    bob eck Member Posts: 930
    temp tank

    we sell fiberglass holding tanks 40gal 80gal 120 gal put your cold winter water in one of these units go fro 40*F to 60* or 65*F great tank
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