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  • Does convective "instant" hot water work?

    If I provide a return flow pipe from below our kitchen sink, will natural convection provide "instant" hot water at the faucet?

    Hot line is insulated inside foam insulation tubes.
    Kitchen sink/dishwasher is on its own branch.

    50-gallon water heater in basement. Return Tee below sink would be 5' 4" higher than top of water heater.

    Can I remove the water heater drain valve, install a TEE behind the valve and connect the return line at the bottom of the water heater?
    Or can I connect it to the cold water inlet tube at the top? (But would the water in the descending tube become too hot and not create convective movement?)

    Thank you.

    Robert
    Last edited by Robert Gift; 05-07-2010, 01:46 AM.
    I'd take an educated guess - but I'm unqualified.
    It ain't just soot, it's paydirt.
    "I swear, wherever Gift goes, argument follows." -Youtube comment

  • #2
    Re: Does convective "instant" hot water work?

    ...this vid may help some.

    http://www.wonderhowto.com/how-to-ho...r-233706/view/

    Comment


    • #3
      Re: Does convective "instant" hot water work?

      it does work very well. but the higher the loop the better the transfer. also a check valve will be reguired so it doesn't draw from the cold. a small 1/8'' hole in the flapper will help with the minimal flow generated by the thermal differental.

      rookie plumber is an expert in thermal loops.

      rick.
      phoebe it is

      Comment


      • #4
        Re: Does convective "instant" hot water work?

        Thanks, Half.
        Can't afford the circulation pump.
        Also, our kitchen sink would not benefit because its branch begins at the water heater.
        I'd like to do this just for the co$t of 1/2 inch rigid CU I bought at a garage sale.
        In the video he does not mention how one gets a control wire from an upstairs vanity to the basement pump.
        I'd take an educated guess - but I'm unqualified.
        It ain't just soot, it's paydirt.
        "I swear, wherever Gift goes, argument follows." -Youtube comment

        Comment


        • #5
          Re: Does convective "instant" hot water work?

          Do I.nstall the check valve at the water heater?
          That would beasier.
          Have never seen one.
          Must it be verticle so the valve flap hangs down and is forced closed by upwards water flow?

          Can I unscrew the drain hose bib and connect the return line there?
          Thanks PlumbeRick.

          PlumBob.
          I'd take an educated guess - but I'm unqualified.
          It ain't just soot, it's paydirt.
          "I swear, wherever Gift goes, argument follows." -Youtube comment

          Comment


          • #6
            Re: Does convective "instant" hot water work?

            the check should be a wye pattern installed horizontal and feeding/ returning to the tank via the drain bibb. install a 3/4'' brass tee to to connect the return to and still allow a hose bibb. you should also install a 3/4'' ball valve at the heater between the tank and the tee. this way you can shut off the water to the tank and flush out the return to get the system in motion. the air needs to flush out and the pipe brought up to temperature.

            the higher the loop, the better the circulation you'll have.

            rick.
            phoebe it is

            Comment


            • #7
              Re: Does convective "instant" hot water work?

              Thank you, PlumbeRick.

              Must I drain the water heater?
              Can I shut the inlet and outlet valves at the top of the tank and unscrew the drain hose bibb and quickly replace it with a capped pipe?
              Or will water coming out create a vacuum which could damage the 50 gallon tank from partial implosion?

              Otherwise, I may wait until we return from a 3-day work trip. I'd turn off the gas and use the hot water so heat is not wasted.
              But hate to flush 50 gallons down the drain. Wish I could at least water the lawn with it.

              When I replaced my girlfriend's water heater, at least I was able to drain it with a garden hose into her back yard.
              It sprung a leak the morning she was to fly somewhere. SO LUCKY!
              Now she and we turn off the house water if we leave. Sprinkler water is still on.
              Last edited by Robert Gift; 05-08-2010, 09:13 AM.
              I'd take an educated guess - but I'm unqualified.
              It ain't just soot, it's paydirt.
              "I swear, wherever Gift goes, argument follows." -Youtube comment

              Comment


              • #8
                Re: Does convective "instant" hot water work?

                robert, in your case it's not bad to drain the heater and flush it out. make sure the heater is clean and the 3/4'' port open all the way.

                for me i can remove the hose bibb and install a brass nipple and ball valve and lose less than a cup of water. but i suggest you drain yours clean.

                remember you need a ball valve between the tank and brass tee. this allows flush out the return line and isolate the heater.

                rick.
                phoebe it is

                Comment


                • #9
                  Re: Does convective "instant" hot water work?

                  Originally posted by PLUMBER RICK View Post
                  robert, in your case it's not bad to drain the heater and flush it out. make sure the heater is clean and the 3/4'' port open all the way.
                  for me i can remove the hose bibb and install a brass nipple and ball valve and lose less than a cup of water. but i suggest you drain yours clean.
                  remember you need a ball valve between the tank and brass tee. this allows flush out the return line and isolate the heater.
                  rick.
                  I regularly flush the water heater by fully opening the hose bib valve to create the greatest flow to scour the tank.

                  Just picked up the one-way check valve. 3/4 inch is smallest they have.
                  Appears that I should mount it vertically so the flap hangs open by gravity.
                  Otherwise, if mounted horizontally, would the delicate convective return flow be stopped by the metal valve flap if it must push against it?

                  Thank you.

                  Robert
                  Last edited by Robert Gift; 05-09-2010, 05:37 PM.
                  I'd take an educated guess - but I'm unqualified.
                  It ain't just soot, it's paydirt.
                  "I swear, wherever Gift goes, argument follows." -Youtube comment

                  Comment

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