Pressure relief valves / water heaters

[sunlover19]

Can you use a standard pressure relief valve from home depot or Lowes or is there a difference between home or RV ones,  current one shows 150 psi /210 degree rating.  

[dickandlois]

14 minutes ago, sunlover19 said:

Can you use a standard pressure relief valve from home depot or Lowes or is there a difference between home or RV ones,  current one shows 150 psi /210 degree rating.  

This is the standard set for the pressure release valves on hot water heaters.

        Pressure Relief Settings Questions regarding relief valve settings frequently come up. For some years, 125psi was the standard setting. Today 150psi is considered the standard. The history of the 125psi setting stems from a water heater standard which formerly stated that the working pressure of the water heater tank would be designated at 42% of the test pressure. As most heaters were tested at 300psi, the working pressure figured out to 127psi. Thus, the 125psi valve became the standard setting. However, the water heater standard was changed to allow the working pressure to be 50% of the test pressure, resulting in the change to a pressure relief setting of 150psi. Under no circumstances should the relief valve setting of the valve exceed the working pressure of the tank, as this would violate all heater warranties and codes.

Rich.

[wildebill308]

Yes, I would recommend taking the old one with you. 

Thank Rich, for the great explanation.

Bill

[sunlover19]

Thanks for the great information, I will pull it out and check it when we get ready for the next trip. 

[rossboyer]

You will probably find that the body of the valve for an RV water heater is shorter than the ones for residential use. The residential one usually will not allow the door to close completely. 

[manholt]

Goggle PPL in Houston, TX. Parts!

[desertdeals69]

If I remember correctly the RV valve is a 1/2 pipe thread and the residential valve is 3/4 pipe.

[wildebill308]

21 hours ago, sunlover19 said:

Thanks for the great information, I will pull it out and check it when we get ready for the next trip. 

Not shure what "I will pull it out and check it" will do for you? The only checks are done with it installed. Is it leaking? if not it  is good. Does it open when you activate the preshure release lever? if it does it is good. Does it seal up and not leak when closed again? Then it is good.

Bill

[rayin]

1 hour ago, WILDEBILL308 said:

Not shure what "I will pull it out and check it" will do for you? The only checks are done with it installed. Is it leaking? if not it  is good. Does it open when you activate the preshure release lever? if it does it is good. Does it seal up and not leak when closed again? Then it is good.

Bill

What Bill said, X2! If your valve is leaking, when you remove it, soak it in vinegar for a few hrs. Re-install and see if that corrects the leaking. If not, you only wasted a few minutes of time and 1C vinegar, then you may spend money for a new valve.

FWIW, they usually leak when the air pocket/pressure cushion  that is supposed to be in the top of the tank is absorbed by the water. Your valve removal, or simply opening the valve handle, plus draining about 1G of water, restores the air pocket.

[campcop]

If the valve is seeping, sometimes opening it and letting is snap closed a couple of times will remedy the seep. Also as mentioned, make sure there is an air pocket in the tank.

[sunlover19]

I think I may just replace it anyway and check the anode rod at the same time since the coach is 15 years old, I think the anode rod has been replaced when the PDI was performed when we bought the coach 2 1/2 years ago. 

[rayin]

The anode rod (Atwood brand does not use an anode rod) should be replaced when it is 1/2 gone/eaten away. That normally happens at least once a year, especially if you leave water in the tank during storage. When you remove both drain plug and over-pressure / relief valve,  use  an water heater flushing rod to clean out the bottom of the tank, you may add more water via the pressure relief valve opening too for additional aid in flushing.