water heater leakin pressure release valve

Most likely lost air pocket as mentioned, Home Depot does have the relief valves that fit. I got mine there, same part number. :)

Air pocket there by design for 'pressure control' ......water expands when being heated

Subject gets beat to death.Dripping relief valve

Like pulsar and wa8yxm said....re-establish the air trap.

Might not be the valve.. Before you go tossing money at it try this procedure.

1: turn off heater.. Wait as long as you can.
2: Shut off water to heater, Either use the bypass system or turn off water to the RV (Both city and on-board pumps).

3: Remove drain, NOTE: I like to pipe the flow out past the side wall of the RV.
CAUTION hot water under pressure

4: Open TPR (the Release valve) to increase outflow.

5: When outflow stops, close TPR and replace Drain plug, IF SURBURAN or other anode using heater inspect anode while you have it out and if in need of a new one, Now is the best time.

6: Restore water flow to heater and let fill.

7 REstart heater

Now see if it still leaks.

Water heater is also an acumulator tank and over time the air cushion is absorbed into the water and vanishes, leading to leakage at the TPR as the water heats, due to overpressure .

It is not uncommon for the pressure release valve to "weep." The weeping occurs when the air gap at the top of the tank is lost.

If this is your problem, it can be corrected by the following steps, when the water in the tank is cold.

Turn off the water supply (pump or city water).

Open a faucet to release pressure.

Pull the handle on the valve straight out.

When the water quits flowing, let the handle snap shut

Close the faucet and turn on the water supply.

I don't know that this is your problem, but should be checked before replacing the valve.

Tom

Replace only as needed and you need a new one. Typically the T&P safety valve is a bit smaller than a home unit so you may need to order one as Home Depot probably does not have it.

Precautions? Let the water heater cool overnight, turn off water supply, and verify no hot water pressure before you unscrew the valve.

I also recommend a small expansion tank to reduce pressure issues. Shurflo makes one for RVs.