Hot Water Pressure Relief Valve

Very simple...unscrew the old one, and replace...Use a couple of wraps of Teflon tape on the threads.

Home Depot, Lowe's.

Okay thanks, I have already tried to turn but couldn't move?
The heater is about 15 years old and runs very good.
Didn't know if there was some secret method of getting out besides muscle.

Rambler

As the other person said, Roughly as hard as hooking up a garden hose to the park water spigot.

TURN OFF WATER (or bypass the water heater) turn off heater, Remove drain plug and replace with a short tube so as to get water out past the edge of the RV. remove TPR valve (unscrew) go to Lowes, home Depot, Sears, Joe's hardware, most any plumbing supply, Hand to customer assistance clerk, get new one, pay, screw back in (Brass should not need tape or putty but you can if you like) remove drain tube, replace plug (See above comment applies to nylon as well)

Restore water, restore power.

Rambler wrote:
Okay thanks, I have already tried to turn but couldn't move?
The heater is about 15 years old and runs very good.
Didn't know if there was some secret method of getting out besides muscle.

Rambler

well 15 year old heater the T&P valve could pretty well attached to the tank it's self. May take a bit of muscle to break it loose.

I discovered the hard way (after paying for a replacement to be installed).....

That when my water heater initially heats up, if you are on the pump and it is ON and all the faucets remain closed during the heat-up (about a half an hour)......the extra pressure of the heated water is enough to make even a properly operating relief valve leak a little bit.

You can prevent that by shutting off the pump until the water heats up and crack a faucet open.

And let's hope that the amount of muscle required to remove the valve won't also damage the tank.

Before you replace the t&P valve try the following;
Your tank needs an air pocket at the top or else it may leak so,

Get a can of PB BLASTER and spray inside the drain opening then
turn off water supply and open a hot water faucet that is higher than the heater, now go out to the heater and open the T&P valve until water stop draining out
Spray inside the drain with PB BLASTER again you are okay if some gets into the heater, you are trying to spray the sealing surfaces which may be rubber, then close T&P valve
Now go inside and close the faucet and lastly turn on water and after the heater is filled start the heater. Do not open faucet to purge air

This may save you a lot of grief takes about 10 minutes

15 yrs old so chances are T&P Relief Valve has built up enough scale that it is NOT a matter of re-establishing the air pocket. Time to replace.

15 yrs old it is well stuck

Try 'tightening' first then try removing. Might have to work back/forth to get it to break free.

Remove the exhaust shield so you can get better access.
And if you have a propane torch slightly heat tank area around the valve...but stay away from valve...it is brass and will absorb heat quickly (making it harder to remove)

Use a breaker bar for extra leverage to remove old one.

15 yr old T&P is a 1/2" NPT-------Atwood changed to 3/4" NPT when they changed design (2004)

Darsben 1

Is it really ok to get some PB Blaster inside the water heater? You ever smell the stuff? I wouldn't want that stuff in my heated water supply.

I would just crank on it. I suggest all these closed water systems should have a small expansion tank instead of relying on the air bubble in the water heater tank.

If you have the smaller style make sure you have a place to buy one. Home store may not have it.

ernie1 wrote:
Darsben 1

Is it really ok to get some PB Blaster inside the water heater? You ever smell the stuff? I wouldn't want that stuff in my heated water supply.

It has not bothered me but YMMV. If you want do not spray with the valve open.
I guess a little does get in but the hot water will wash the PB Blaster out or if it works you can heat the water in the tank and then drain it to flush out the tank. If the valve is stuck I would do it an a heart beat to avoid ruining tank. If it does not work once the valve is off run water to rinse tank if you think the PB Blaster smell if any would be objectionable.