Pump is short cycling
We have a residential irrigation system running off a shallow well pump. The pump delivers about 20 gal/min. The pressure switch on the pump is set to turn-off at about 60 psi. The original design was done so each zone handles a bit more than 20 gal/min at 60 psi. As such, when a zone valve opens, the pump just runs without a need for a storage tank. It's operated like this for about 9 years now.
This year I've noticed that the pump will short cycle on certain zones. The problem isn't always consistant as multiple attempts at turning on a zone will sometimes work as expected, and sometimes result in short cycling. All the heads are spraying water, so I don't think the problem is at the heads.
I suspect the problem may be zone valves (irritrol) which aren't opening fully all the time. Does this sound right? How would you diagnose a faulty zone valve? Can they be serviced, or is it better to just replace them. What else could it be?
