Trying to replace the expansion tank on our electric water heater. I bought a water pressure gauge and tested it on the outside faucet, as well as at the water heater and I get a reading of 140 psi. I lowered the wpv and barely get any waterflow, but the gauge reads 120 psi. The wpv I have is a Wilkins br4 series. Not sure if I’m doing something wrong, or if I have a faulty gauge or what.