Debris caused PRV to fail.
A guy I know tore down and old house and built a home 7 years ago. The water service from the city side was reused and all the plumbing for the new house is new including the PRV.
Recently the City came out and replaced the 30 year old 3/4" water meter. It only took them a few minutes to remove the old meter and put the new one in, they turned on the setter and purged a little air then flushed some water and from an outside hosebib.
After that there was a lot of water hammer and the pressure was high so he called the City. The City came out and checked everything out, they even put a pressure gauge on the hosebib and it read 100psi. They said there was nothing they could do since the problem was on the private side of the meter.
My buddy called a plumber and the plumber went through a few things then ended up replacing the PRV in the crawl space. The plumber said the PRV had dirt in it and that's why it failed and caused the water hammer.
I'm curious as to what caused the problem. Could it have been something on his side or is the City liable? How would I prove it? The plumber took the old PRV.