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

I just opened up the valves for the season and the test cocks. That all worked fine, but then I went back inside and heard what sounded like a loud groaning sound going off every 15 secs or so. I pulled the cover off the control box and saw that one of the connections going to a line (I guess - I'm not well versed in this stuff) seemed to be leaking with a surge of sorts - like a heartbeat - about every so often. When I turned off the one of the two water valves (not part of the control box - separate piece), it of course stopped. My layman's guess is that the connection between two pipes in the control box someone loosened over the winter, and as the water pressure builds, it releases periodically. I have no idea how to attack this problem. Suggestions? I've never dealt with sprinkler issues so should I just go straight to the yellow pages?