high dynamic water pressure - what is normal?

At my home, I have ~40psi of static water pressure on the house side of the regulator (I have a gauge on it). The water on the street side of the regulator is ~110psi. The gauge has a "max" indicator.

Over a period of ~1 day, somewhere it is peaking out at ~ 110psi (dynamic max pressure). I don't know if this is peaking at 110psi for 1 second, or minutes... just know it hit 110psi at some point.

Is this normal?

thanks

Do you have presure reduducing valve at your main incoming.

Scratch that replace prv.

Normal on a city water main is whatever the city put into it. That's way too high for a home, that's why you have a PRV. 40 psi is on the low side of normal pressure for a home, it could be set up to about 60 psi if you wish a little more. For what it's worth, my city main is usually 90 psi. I wouldn't worry about the high pressure in the city main.

If you are saying that the house side gets to 110 sometimes, that is no good. Either the PRV is leaking by, or you have expansion caused by the water heater. New water heaters often necessitate an expansion tank.

pressure

If the PRV was defective the pressure would increase to the city pressure and stay there until a faucet was opened, and then it would start to increase again when it was closed. Your situation sounds more like expansion from heating water. That will only occur when the water heater is operating, and will diminish to the normal pressure, and 40 psi is well below normal, and stay there once a faucet is used.

There seems to be a misunderstanding about you problem. When I read you question, I thought you were saying your household pressure was 40 psi and the city water main pressure sometimes reached 110 psi. However, others think you are saying the house pressure sometimes rises to 110 psi. If that is the case, then what is happening is your expansion tank has gone south. If you don't have an expansion tank, you definitely need one since a PRV creates a closed system. When your water heater heats water, the water expands. A PRV prevents the expanded water from being absorbed by the city main so the pressure in you house will rise. This pressure often will exceed the TP valve limit of 150 psi on the water heater and cause it to trip. The cure for this problem is an expansion tank added in the supply line after the PRV. The pressure inside the expansion tank is set to match the setting of the PRV.