Water heater pressure relief valve

[nephi007]

Howdy. Should the pressure relief valve in water heater compartment when opened release water or just air. Hooked up to city water it releases water only. Advise please.

[Skip426]

Using the relief valve to vent ALL the air out of the tank , removes the expansion area in the tank and the valve will drip when the water is hot .

Check you water heater's owners manual .

[WillT]

What I do is when water heater is empty is this: Make sure the relief valve is closed, (actually, I never open the relief valve). Then hook up to city water and turn on and you will hear water running even with all faucets off. This is the tank taking on water and the air space being compressed. Once that stops, I open the shower hot water faucet until air stops coming out and water is flowing. Next I briefly open all other hot water faucets to purge the little air left in pipes. Then I am good to go. This method seems to fill the tank with water but keep a pocket of air for expansion at the top of the tank. This works flawlessly for me on my Suburban water heater at least.

[Old-Biscuit]

It releases WATER....hot water/scalding hot water (140*F when t-stat opens)

to properly fill water heater
Connecft city water or turn pump on
Open nearest sink faucet hot side----this will accomplish 2 things
1) allow water heater to fill to normal level
2) bleed air out os hot system

doing this allows for the natural formation of the Air Pocket at top of tank
Water swells when heated....W/O that air pocket presure will increase cause water can not be compressed/air can
Increase in pressure can be high enough to cause the T&P Relief Valve to 'weep' when water is heated

To re-establish the Air Pocket
*turn water source OFF
*Open facuet Hotside to relieve system pressure
*Open/Hold open the T&P via lever until water stops flowing out
*Let T&P SNAP close
*Turn on water source
*Close faucet when water flows

[nephi007]

Howdy. Ok all good info. By the way the pressure relief valve is threaded I hate to assume its’ purpose so I am asking here.

[Old-Biscuit]

Originally Posted by nephi007

Howdy. Ok all good info. By the way the pressure relief valve is threaded I hate to assume its’ purpose so I am asking here.

The threaded opening so a discharge pipe can be installed to route the Flow away from the area.
*Residential Water heaters....same T&P used hence the threads

[nephi007]

Howdy & thank you for explaining .

[charliez]

I actually stopped my former FIL from drilling a hole in his WH. Yes, it was filled, hot and under pressure and on. I should have just let him and stayed back with a video camera.



Don't ever try this.

[1320Fastback]

Yes if you are hooked up to city water or have the water pump on when using the fresh water tank and you open the pressure relief valve water will come rushing out.