I purchased an 89 Catalina 34, hull 885. Having an issue with my Seaward 6 gallon water heater. The check valve for the cold water coming into the water heater keeps exploding if I leave the water heater switch on for too long (~ 1 hour) or if I run the engine for a couple of hours. I replaced 4 valves so far using different brands to make sure its not a one brand issue, but none have worked. I also replaced the pressure release valve, just in case it went bad, but in vain. I asked a professional opinion and was told I need to install an accumulator to fix this problem. I thought the accumulator is only needed if the water pump requires one. Any thoughts?