[Laker14]

Originally Posted by jrref

Technically you are supposed to pre-pressurize the expansion tank to the supply water pressure to your home or the tank will fail prematurely. It says this in big print in the expansion tank instructions. That said if you pressureize the tank to something close to the inlet pressure you should be fine. Remember your water pressure is going to vary during the day anyway. You just want to avoid streching the internal membrane to it's limits causing it to fail. As far as pressurizing and or measuring the pressure in the expansion tank, closing the the water supply valve to the hot water tank and opening the hot water in the house should release the pressure in the expansion tank but if you have an electric hot water heater i would open the circuit breaker to the tank during the process just to make sure the heating elements do not come on with no water on them.

thank you.