The water pressure in the house varies when a faucet, shower or commode flushes. When the other faucet, shower or commode finishes filling, the water pressure will increase. I have measured the water pressure. It is 50 lbs without any use in the house. When two faucets are on it may drop to 20 lbs and then go to 40 lbs when one is turned off. My question is "could the pressure regulator not be working properly? I have PEX plumbing.