I have an issue that has been getting worse in my house. Every time we flush the toilet or take a shower we are getting pipe noise by the pressure regulator valve. Shaking and moaning noise by the PRV and stops after a few minutes. I ended up picking up a water pressure gauge and with nothing running it reads at 85 PSI and when I flush a toilet it drops down to 45 PSI. Is this normal?

How old is your house and what material are the water pipes? Copper, galvanized, or plastic? 45 PSI is the normal house pressure. If you have galvanized pipes iron oxide buildup will reduce volume which will also drop your pressure. Back to you, Tom

It was built in 2000 and has copper pipes. When it does drop to the 45 PSI the pipes make some loud noises for a few minutes. I was under the impression that the Pressure regulator valve would only drop 10-20 PSI instead 40 PSI.

Is the shaking worse next to the pressure regulator? If not where? Describe the noise, is it a rattle, banging or thumping sound? Can you furnish more details? Back to you, Tom