Thinking of adding a pressure reducing valve (PRV) to reduce my home's water pressure. I understand that I'd need to add an expansion tank to the incoming cold water line of the domestic hot water heater (DHW).
My question is should I size the expansion tank for the system pressure before installing the PRV or after installing the PRV? By sizing for original pressure I have the capacity to handle expansion in the event the PRV fails.
Also related question... Do I pressurize the tank to the system pressure before or after the PRV for the same reason of possible PRV failure?
I'm probably just going to go with a larger expansion tank that will handle the current incoming pressure since it's not much more expensive and having a larger tank won't hurt anything but I'm curious to know the answers and reasoning.
Here are the stats:
Current pressure around 92 PSI Desired pressure 65 PSI (maybe a little more like 68 PSI) HW capacity 40 gallons HW temperature 125F