Gravity hot water recirq piping

Couderay

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?

bruce_21

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

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

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

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

Why does the return loop need to be more than 1/2?
Thanks,
Tim

Gordy

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