Hot water shuts off to house until I open drain valve to relieve pressure. Why?
As the title suggests... this has happened 4 times since I installed a Rheem Performance Platinum 65 gallon Heat pump water heater last year. It typically occurs when our clothes washer is pulling hot water. The rest of the house will suddenly lose hot water, and the washer will also eventually throw an error code as the hot water will shut off to it as well.
My only solution is to go downstairs to my water heater, shut off the cold water to the water heater, and open the drain valve on the bottom to relieve a huge rush of pressure. Once that occurs, I then close the drain valve, open the cold water inlet valve, and hot water is restored to the house.
I'm at a loss. My pressure relief valve is not leaking out any water, and performing a test on the valve reveals that it still works just fine. Is there some sort of internal 1-way trap door on the hot water outlet side that's getting blocked? I input and output the water from the top connections (there are side connections available, but they are unused). I'm not using a recirculation pump, and I have an expansion tank installed (though it's the smaller 2.5 gallon model - might need to move to 4.5) that I installed new with the water heater. There is no leak detection or auto-shutoff feature in this model.
Any thoughts? I was going to contact Rheem, but haven't managed to yet. Thanks!