From the Raritan Web Site:
If your water heater’s pressure relief valve is dripping, it could be due to several reasons. One common issue is that the rubber seal in the valve may have worn out over time. This part can be replaced with #WH3. The relief valves on Raritan water heaters are set to activate at either 75 PSI or 210° F. If the pressure or temperature exceeds these limits, the valve will open to release the excess.
For Raritan water heaters with heat exchangers that use engine coolant, ensure that some coolant is diverted through a bypass valve to prevent the water temperature from exceeding the relief valve’s limits.
If the pressure relief valve you’re seeing is rated above 175 PSI, it indicates that a higher-pressure valve was installed, which could be due to the system’s requirements. In a Liberty system, expansion is managed by the accumulator or expansion tank, provided the bladder pressure remains between 20 to 30 PSI. If this bladder pressure is lost, the system becomes closed, similar to a hydraulic system. In this state, any expansion due to heating will increase system pressure, and with nowhere else to go, the excess pressure might cause the relief valve to open. If a high-pressure valve like a 175 PSI one is installed, it will hold the pressure until it reaches a critical point, potentially causing the system to fail if the pressure builds up too much.
For more information, check the owner’s manual or contact Raritan Technical Support.
I firmly believe that anyone using a 175 PSI pressure relief valve should replace it immediately. The 75 PSI valve is essential for safeguarding the entire system, regardless of whether the expansion tank is functioning properly.
It’s impossible to determine the exact pressure that was reached in my tank or if the 175 PSI valve ever activated on its own. However, it’s clear that the pressure was significant enough to cause noticeable deformation of the tank. Even if the pressure was below 175 PSI, it was substantial, given that a 20-inch tank could experience around 55,000 pounds of force at 175 PSI.
Although my tank didn’t rupture, it did expand vertically by 2 inches. What’s remarkable is that the plumbing system managed to withstand the pressure without any leaks, which is quite impressive for plastic plumbing.
Additionally, there is a mysterious stain behind the heater that remains unidentified.
I wasn’t able to observe the heater replacement in person, so I handed my camera over to Bill Daughtery, who took the photos. I would have liked to be involved in the repair, but unfortunately, I don’t have a garage of my own. I do, however, envy John’s barn.