Water Heater Pressure Relief Valve

[soohma]

For the first time this trip, water came out of this valve. I did what the book said, which was to turn off the water at the source until the dripping stopped, then turn it back on. That seemed to work as water didn't come out anymore. But I was afraid to turn on the heater switch again.

My question: The valve itself is quite rusted and the little handle revolves without seeming to do anything. Do I need to have this replaced? (I'm not handy like some of you guys.) Was this a one-time thing and the next time I turn on the heater to get hot water it won't happen again?

Is it safe to turn on the heater?

[markopolo]

That Water Heater Pressure Relief Valve is a safety feature to release excess pressure in the system. Turning it does nothing. Lifting it opens it but be cautious. If the water is hot and under pressure you possibly could be burned.

It is normal for it to drip a bit occasionally. That means it is working. If the dripping is excessive re-introduce air into the water heater tank after the water has cooled. The best way to do that I think is to remove pressure from the system; disconnect from city water' turn off your water pump and then drain some water from the water heater. For my van that would be by unscrewing the anode rod (Suburban water heater). Atwood water heaters have a threaded plastic drain plug.

[WJones]

When you initially fill the water heater at the beginning of the season, it doesn't fill completely with water. There is an air pocket at the top and this air pocket absorbs the pressure when you heat the water.
As time goes by, you can slowly lose the air pocket and when the water heats and expands, the pressure increases and the water comes out the pressure relief valve. You have to recreate the air pocket.
As markopolo said, you have to remove some water from the heater (when it's cold and the pump and city water supply are off.).
I've read you can do this by simply opening the relief valve until water stops coming out. Then close the valve, turn the water supply back on and open a hot water faucet to allow the heater to fill to its normal level.
You will probably be OK for a while, but might have to do it later in the season.

[soohma]

These are great responses. Thank you so much. Now I know what happened is normal. Off on my cross country adventure with confidence now.

[booster]

We don't use the heater much, so we have not had it drool yet. I would think you would be able to reestablish the air cushion by shutting off the pump (no shore connection), opening the outside shower hot faucet, and then opening the relief valve. That should pull air right to where you need it very easily and quickly.