Setting water pressure question

I live in a relatively new home and checked my water pressure today on both hose bibs and it sits around 56 to 57psi with all faucets off. Then I ran a hot water faucet inside for 10 minutes (then shut it off) which kicked on the water heater. The pressure spiked around 73 to 74 psi while the heater was running. It dropped back to around 60 psi within 15 minutes, and then drops a tad lower after 45 minutes or so. Is this OK or should I lower the pressure down some with the PRV? I don't want to have premature leaks due to high water pressure. The entire house is PEX with the except of the copper tubing that comes out the walls where the shutoff valves are located. Just want to make sure I have an acceptable pressure rating especially with it going up to near 75 when the water heater is working.

The rise in pressure is normal. Your pressure is well within safe range.

Do you have an expansion tank? If not, there is no way to control how much the pressure increases from the water heating. All reducing the static pressure will do is give you a poorer flow from the faucets, but the pressure could still increase to 75 psi, or higher, depending on how much hot water you use and the temperature the tank is set for.

I don't have an expansion tank, but I was hoping that since the pressure was never any higher than 75 psi when the w/h was running full blast then I was probably OK without one. I've always kept the water heater on it's lowest recommended setting, so the water temp never get scalding hot and it helps keep the gas bill from going crazy.

I just want to make sure I'm still within a safe psi range because I don't know at what pressure you would need to get an expansion tank installed.

While you may not have a prv, it sounds like you may have a check valve in your supply (often installed by the water company). So, to solve this problem, install an expansion tank. Your pex lines are acting like an expansion tank and you are putting more stress on them. Probably not a big factor, but it will also wear on the supply hoses to the washing machine and faucets. your water heater may last longer, too.

There is a PRV on my side of the water meter, and it has a range of 25-75 psi according to the tag. It was set on 45 psi when I first moved in and I told the builder that I didn't have enough pressure to wash my car. Therefore the contracted plumber came out one day when I was gone and adjusted it, but I never followed up to see what he set it to. Many more houses have been built in recent months in this neighborhood, so I decided to check it over the weekend and the numbers I posted above is what I currently have going on. I may scale it back to 50 psi just to try and keep it under 70 when it maxes out.