Thursday, December 8, 2022


Check valve and P&T valve on water heater explained


gary-736Dear Gary,
When I run the water pump on my newish coach, water runs out of the area where my water heater is. After inspection, the water is running out of the check valve in my water heater. I spoke to a friend and he advised me that I just needed to replace the P&T valve in my water heater. I have only owned this unit for about six months and never had this problem when I first purchased it. So, is it as simple as just replacing the P&T valve or check valve in my water heater? What would have caused this valve to go out? I have noticed whenever the water pump is on, water just streams from my water heater. —Kevin

P&T valve

Dear Kevin,
The check valve and the pressure and temperature (P&T) relief valve on the water heater are two different components. Where you see the water streaming from the heater is going to reveal the biggest clue.

The P&T valve is located on the exterior of the water heater, behind the access door. If water is profusely emanating from the P&T valve, it may need replacing. If it just drips a small amount but at a constant rate, try opening then snapping shut the lever on the P&T valve a couple of times. Oftentimes, tank residue or mineral deposits can prevent the valve from fully seating. Take care to only do this only when the water in the tank has cooled! The system can be pressurized by the water pump, but be advised, you still may get a little damp! It IS a normal occurrence, however, for the P&T valve to seep a little during the actual heating cycle, but certainly not enough to keep the water pump running. Also, while you’re out there on the outside of the water heater, be sure the drain plug is not leaking. 

Check valve

The check valve(s) (you may have two), however, are located on the back of the water heater, accessed from inside the coach. It’s possible a fitting or one of the check valves may have ruptured, cracked or otherwise been rendered faulty. Some of the cheaper, plastic check valves fail at a higher rate than the brass valves. But it’s impossible to know until you gain access to the rear of the water heater from the inside. A close inspection of all the fittings and connections will reveal the location of the culprit. Hopefully it’s just a leaky P&T valve, but don’t overlook the fact it could be leaking from any component at the back of the heater as well. 

A worst-case scenario would be a ruptured inner tank, but that is unlikely on a relatively newer rig. After replacing the offending component, be sure to have the fresh water distribution system leak tested and the air cushion reestablished on top of the water in the heater.

Read more from Gary Bunzer at the See Gary’s videos about RV repair and maintenance.



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Richard Schaumburg
4 years ago

I understand an air cushion and the reason for it, and like Mr. Andrew’s question, how doe one create it? Is an automatic event when the tank is re-filled when put back in service?

4 years ago

Gary, no mention of creating an air cushion which would probably solve this writers problem. How come?

Charles Andrews
4 years ago

I hear talk of an air cushion in the water heater
What is it Nd how do you establish it?