PRV constantly "pumping"
Just started up the irrigation system for the season here in CO. Had an irrigation guy out checking on a bad solenoid for one of my 6 zones. In starting up several of the zones for the first time, the pressure reducing valve started making this pumping noise. Anyway, irrigation guy thought it was the backflow preventer and was all normal and "no worries, that is what it's supposed to do, it can do it all day," etc. His theory was that if water was running elsewhere in the house (washing machine, shower etc) it might cause this. Problem is that (1) we never noticed this before in 18 years we've owned the house, and (2) the sound was coming from the PRV not the backflow.
The irrigation line comes off the main water supply from the city before the house's main PRV, which is why we have one on the irrigation system here. This PRV pictured is brand new as of last season (irrigation guy who was out fixing a bad solenoid was the guy who installed it when my last one busted last year).
Anyway, the PRV only seems to do this on 2 of my 6 zones. One zone runs to a landing strip between sidewalk and street on the side of my house (we have a corner lot) and the other zone is a long drip line with tons of outlets along the way for various trees, garden bed areas, etc. The other 3 zones where the PRV does not do this are two yard zones with tons of heads and one small drip zone.
So what do y'all think is happening here? Irrigation guy is wrong, correct? There is something else going on other than a backflow issues, right? if it was backflow, what would cause that to happen? We have never had this issue before. Is water pressure too much for the PRV? Too little?