I recently had a pressure reducing valve installed to fix our 105 psi static pressure. We also had an expansion tank installed, and it is the appropriate size for our two hot water heaters. I adjusted the PRV to about 60 psi, and I have noticed the pressure will climb to about 65 psi after someone uses the shower, bath, and some other times throughout the day. The pressure immediately drops back to the desired setting of about 60 psi when a faucet is briefly used, and the pressure tends to hang right around 60 psi for the most part. The instructions state that this is natural and that it may happen when the water heater runs. It also states that a pressure relief valve or expansion tank must be installed, but they will not prevent a pressure rise, but should limit it to a safe level. I understand the need for the expansion tank with the now closed system, but is this slight increase normal? Will this harm the expansion tank since the bladder is set at 60 psi? I really want this to be a trouble and worry free system. Any advice is greatly appreciated.