SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

System works ok with water but when I went to blow it out this year heads popped up for zones that weren't selected. I am using a small compressor with a pressure tank and wait 2 minutes between zones for the compressor to recharge the tank. But this year I can't get the selected zones to blow out because of the other zones leaking. The system is about 15 years old and I have replaced a few things over the years but otherwise was working ok. Does it take higher pressure for the valves to shut off tightly?
I blew out some of the zones a few days ago (the above ground hose bibs but not the in ground sprinklers) and it seemed to work fine for that. I did have a bit of trouble and as I recall I ran water through the zones I had trouble with and that seemed to allow me to blow out the system. Maybe a bit of crud in the valves but seems unlikely on multiple valves?

I increased the size of the hose from the compressor tank to the RPZ valve and am getting much better results. Apparently the valves need a certain amount of pressure to shut off and the effect gets worse as things get older and have more use. Just a guess.