I recently replaced my water heater.5 minutes after lighting burner,water started to trickle out of my pressure relief valve. I swapped the valve with the one of off my old heater,It also trickled.the GE tech line said I may need an expansion tank. My house had a tank in it when I bought the house.I don’t know how to test it. I have no paper work on the unit.I tried to check the pressure at the bottom shraeder valve and water came out.Is my diaphram broke? How is it recharged?