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Thread: Correct size for Bosch AquaStar tankless water heater?

  1. #1
    DIY Junior Member KarenTheBold's Avatar
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    Nov 2004

    Question Correct size for Bosch AquaStar tankless water heater?

    I'm interested in replacing my tank water heater with a Bosch AquaStar. It would serve a home with 2 baths, and an in-law unit with bath and kitchen.

    The smaller model ($500) says it provides hot water for "one major application" at a time. The larger model (close to $1000) provides for two and a half.

    I'd welcome hearing opinions about this heater and about sizing.


  2. #2
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona

    Default heater

    This is a case where too big is no problem, but too small is a lifetime problem. You will either love it or hate it. There is no inbetween with a tankless heater. Be sure that the gas line is adequate for whichever you buy and that the flue is either big enough or can be increased without a major home remodeling.

  3. #3
    Plumber Deb's Avatar
    Join Date
    Sep 2004

    Default Deb

    Actually the way these heaters are rated is that they will raise a certain quantity of water a certain number of degrees. If your water is considerably colder or warmer it affects the gpm and the temperature. I have had to install valves to "throttle down" the hot water flow as the heater was not capable of raising the temperature of the quantity of water the fixture was putting out above very warm. Do not consider the smaller one. I would even say that the larger one is pushing it with a separate residence to consider. I would urge you to check out some other makes and models also.
    The Pipewench

  4. #4
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    The Aquastar 125 gives 2.5 gallon per minute. Enough for a good ( but as long as you want!) shower. Washing machine OK. Dishwasher OK. Only ONE of these things at a time. Tub fill would be very slow if you wanted it hot.

    The model 240 gives 5 gallon per minute. You could do 2 things at once, except the tub.

    Your situation would seem ideal for multiple units. This may be pricey depending on where they could be located.

  5. #5
    Master Plumber master plumber mark's Avatar
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    Feb 2005
    indianapolis indiana - land of the free, home of the brave....
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    Talking master plumber mark

    why do you want to put yourself through all this trouble and extra expence???

    before you buy one try to find a competent serviceman in your area and see how soon it would be before he could come out

    ask how much he charges too..

    look under my name for another long winded explanation I made about this subject

    good luck god bless


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