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Gravity hot water recirq piping

Couderay
Couderay Member Posts: 314
Could someone please tell me the best way to use gravity to recirq the domestic hot water and all thats needed. 35' run from last faucett to superstore,8'of heigth(ranch). Does line size matter 7/8" or 5/8" O.D. tubing?

Comments

  • bruce_21
    bruce_21 Member Posts: 246


    You can use 3/8 " tubing. Remove the drain valve from the HWH replace it with a brass nipple, tee and a good ball valve to drain it with, cut in a tee at last fixture and run the tube back to the newly installed tee at the bottom of the tank. I'd insulate the existing hot main and this recirc line.
  • tim smith
    tim smith Member Posts: 2,841
    Gravity return line

    I would watch out for smaller size gravity piping. The resistance to flow will be too great for it to circ. I would feel much better w/ a 3/4 gravity return. Just mho, Tim
  • Couderay
    Couderay Member Posts: 314
    check valve

    Do I need a check valve by the tank and I remember someone saying to drill a small hole in the flapper of a swing check??
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928
    Swing Check

    Yep.

    Ensure that your DHW supply piping maintains at least 1/4" per foot slope away from the indirect. Once the last connection is made to the supply main, maintain at least 1/4" per foot slope back to the indirect.

    With only 8' or so of elevation, use at least 5/8"
    o.d. tube for the supply and never less than 5/8" o.d. tube for the return. 3/4" or larger tube is preferred.

    EEEK!

    Install the swing check at the DHW recirculation return connection such that flow cannot come from the heat source. Drill approx 3/16" hole in the swing check flapper.
  • Tim Gardner
    Tim Gardner Member Posts: 183


    Why does the return loop need to be more than 1/2?
    Thanks,
    Tim
  • Gordy
    Gordy Member Posts: 9,546
    3/8\" return works fine

    I have a gravity recirc set up that works just fine with a 3/8" return line. It was done in the 50's when house was built,house is a ranch style. You don't need alot to promote circulation with a large delta t coming off the water heater.
    Remember you can have ghost flows with in a 1/2" pipe up to the old style compression tanks on a boiler, hence the B&G tanktrol fitting was invented.

    Not to say larger is not better, but you do not need much to promote circulation.

    Gordy
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