Is my Pressure Regulating Valve bad?

[Kiksbutt]

I checked my spigot outside with a pressure guage and it's showing a little under 100 PSI. The only symptom I'm noticing is some wooshing sound in lower level, basement, copper pipes when a toilet is flushed or water is running for long period. It's been like that since we moved into this house circa 2019. Otherwise, no issues or leaks.

I have a 2019 Watkins PRV model 70. I could try to adjust the nut and unscrew counterclockwise to see if it does anything to pressure, but I'm not sure if I need to shut the water off. I don't like messing with water to create a leak. Will water leak if I try to adjust it to see if it impacts pressure? I also have a pressure relief for the heater installed in 2020.
Any thoughts?

 

[Reach4]

Check the pressure at a laundry tap or the drain on the water heater, as you dribble water from a faucet.

Some houses have the hose spigots use water teed off before the PRV.

You should be able to adjust without turning off the water. However turning off the water for your house should not be a big deal. Everybody should know how to do it, and if there is no readily accessible valve, get one installed.