Testing pressure Relief Valve on Hot Water Tank

[George Bokros]

On the new today there was a story about a family whose boiler exploded. Luckily no one was injured. The said that you should test the pressure relief valve not only on your boiler but also on your hot water tank. The installer that installed my replacement under warranty hot water tank opened the pressure relief valve to aid in filling the tank after he competed the install. He told me to make sure I drained the tank as a maintenance task twice a year but said to not open the pressure relief valve as he did because it may not seal again.

After the story on the news I am wondering anyone does test the pressure relief valve on their hot water tank? I have never done it before.

Thanks

[Myk Rian]

but said to not open the pressure relief valve as he did because it may not seal again.

Every time I have tested the valve, I got leaks. I don't do it anymore.
What you can do besides draining the tank, is connect a garden hose to the bottom spigot, and drain a few gallons out of it. That's it. Nothing more.
Once a year is enough.

[Jim A Walters]

+1 on the leaks. I tested mine and it leaked from then on so I had to replace it.

So if you have to replace it after testing, how does one know the new one will work if needs to? Can't test it for fear it will leak too. I'm going with just draining it some once a year to remove any sediment.

Jim

[Todd Willhoit]

I have found some useful water heater information:
www.waterheaterrescue.com

He specifically speaks to the T&P valves here.

I don't think draining water as Myk mentioned will help with the T&P valve, but a full flush is certainly worthwhile in a hard water area like mine.

[Clint Baxter]

Don't go opening the valve unless you're prepared to replace it. As stated earlier, the odds are very high that it won't seal again. And the older the valve, the greater the chance. The valve is there to relieve either an over temp, or an over pressure condition. As long as you don't install a plug in it, it should function as designed.

Clint

[Lee Schierer]

Minerals accumulate inside hot water tanks. Opening the safety valve can disturb the minerals in the valve which can be like grains of sand and then the valve won't seal completely. There really is no need to test one. If your valve starts weeping it should be replaced.

Make sure the valve outlet is plumed toward the floor so that it it does blow it doesn't spray hot water across the room. But also be sure water can't accumulate in the drain piping.

[Curt Harms]

Don't go opening the valve unless you're prepared to replace it. As stated earlier, the odds are very high that it won't seal again. And the older the valve, the greater the chance. The valve is there to relieve either an over temp, or an over pressure condition. As long as you don't install a plug in it, it should function as designed.

Clint

I no longer count on it functioning without being tested. I had to replace our water heater a couple years ago. Turned the water off, connected a hose to drain it and figured I'd open the relief valve to let air in to speed the process. It would not open -- AT ALL! If the gas control had failed open we'd have probably made the news. When I drain the bottom, I also open the relief valve. I wonder if not sealing properly is related to cycling after not having been opened for an extended period. If I do have to replace it, that's far cheaper than having it not work when required.

[Myk Rian]

Mythbusters.
http://www.discovery.com/tv-shows/my...-water-heater/

[Stan Calow]

I have had the drain valve get stuck and leak from sediment caught in it, when it had not been drained for a few years. I cant open that video, but my understanding was that it could only happen if there was a backflow preventer on the water line, preventing expansion from being absorbed by the line pressure.

[Lee Schierer]

I have had the drain valve get stuck and leak from sediment caught in it, when it had not been drained for a few years. I cant open that video, but my understanding was that it could only happen if there was a backflow preventer on the water line, preventing expansion from being absorbed by the line pressure.

That will cause the safety valve to weep. water hammer or banging pipes can also cause the safety valve to leak a few drops, which then evaporate and leave behind minerals. Over time the minerals can build up to where the valve will not operate.

[Stan Calow]

I meant the drain valve at the bottom of tank too, not the relief valve. I understood that exploding water heaters were related to back flow preventers.

[Lee Schierer]

Water when heated expands. A back flow preventer prevents any water from going back from your house to the public utility. When all the faucets are closed and you get a tank full of cold water after a long shower, there is no place for the increased volume of water to go so pressure will increase in your water system. This pressure should be well within the capability of the tank and your piping to with stand. Tanks take several hundreds of psi before they will explode and if you ever watch Mythbusters, making one explode takes a lot of work and every single safety system has to be physically circumvented to explode a tank.

[Jerome Stanek]

Water when heated expands. A back flow preventer prevents any water from going back from your house to the public utility. When all the faucets are closed and you get a tank full of cold water after a long shower, there is no place for the increased volume of water to go so pressure will increase in your water system. This pressure should be well within the capability of the tank and your piping to with stand. Tanks take several hundreds of psi before they will explode and if you ever watch Mythbusters, making one explode takes a lot of work and every single safety system has to be physically circumvented to explode a tank.

That is why they put an expansion tank in to compensate for the pressure.

[Ole Anderson]

That is why they put an expansion tank in to compensate for the pressure.

And a pressure relief valve, just in case.