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water heater installation

Rich | Posted in Energy, Heating & Insulation on November 17, 2007 07:13am

I have a long run from the hot water heater to the kitchen, so we have to run the faucet for a while before any hot water shows up.  Since there is a heated crawl space right under the kitchen, I decided to buy a 6 gallon electric water heater that will tie into the water line right under the sink.  Is there any issues I need to be aware of when installing two water heaters in series?  The existing heater doesn’t have an expansion tank, there are no check valves, pressure reducers or other devices (I don’t even have a water meter.) in the house.

I’m planning to put two tees in the hot water line under the kitchen to feed the heater.  I was told it is a no-no to put a valve in the outlet of the heater, though I’d like to.    I will put a valve on the inlet to the heater and a valve between the two tees, so I can force the water to the heater or bypass the heater.  Any advice would be appreciated.   

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  1. plumbbill | Nov 17, 2007 09:10pm | #1

    I answerd the valve question in the other thread, but will say it again for others to read.

    You can put a vlave on the outlet side.

    I do very large domestic boiler systems. Every boiler has valves on the inlet & outlet side for isolation purposes.

    I'm not a fan of small water heaters placed in series at the point of use, but opinions vary.

    If your main tank has an expansion tank & is sized big enough for both tanks & there is no check valves then 1 expansion tank can handle both. The small water heater will require a pressure relief valve though.

    "If men are so wicked with religion, what would they be if without it?" Benjamin Franklin

    1. Rich | Nov 17, 2007 09:58pm | #2

      Well, thanks, that's good to know.  Maybe that's just a strange code requirement in my area?  Or maybe the guy who told me that didn't know what he was talking about.

      I have no expansion tank in my house.

      Can you elaborate on why you don't like water heaters in series?

      1. plumbbill | Nov 17, 2007 11:03pm | #3

        I prefer circ systems.

        I like to keep as much as possibe in a central location.

        "If men are so wicked with religion, what would they be if without it?" Benjamin Franklin

  2. BillHoover | Nov 18, 2007 02:26am | #4

    A more energy efficient solution is to put in an on-demand recirculation loop.

     

    bill

  3. DanH | Nov 18, 2007 04:26am | #5

    The harm of a valve on the outlet is that if someone turned both off you'd overpressure (or perhaps underpressure, as it cooled) the heater.  Otherwise there's no danger -- just cut power and open the drain or jam the T&P valve open if you turn off both valves.  (Put this on a "NOTICE" and paste it to the side of the heater.)

    If your view never changes you're following the wrong leader
    1. Rich | Nov 18, 2007 05:20pm | #6

      If someone did close both vavles with the heater on, the T&P valve should release any excess pressure, right?

      1. DanH | Nov 18, 2007 05:46pm | #7

        Yeah, and then when the heat goes off the water contracts and the heater tank develops a dent, and the glass on the inside falls off.
        If your view never changes you're following the wrong leader

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