Patrick McDonagh said: This year we have an unusual number of our Toro sprinkler heads leaking. Sometimes replacing the pilot valve soles the problem other times it does not.
We are getting tired of staking off the weepers.
The system is 25 years old is this what I am to expect.
Patrick,
Our system is of similar age as yours and we have also had several weepers the last few years. What I typically do in order to diagnose whether it's a bad pilot valve or bad white valve (bottom valve, foot valve whatever you want to call it) that's causing it to weep is dig up the head and pinch the pilot valve tube with a pair of vice grips (being careful to not damage tube). Dry off the head and if weeping has stopped, it's a bad pilot valve. If it continues to weep, it's either a bad white valve or a damaged can.
If it turns out that it's a white valve, as someone else mentioned, make sure you check the valve seat in the bottom of the head to determine if it's nicked or otherwise damaged. If it is, you'll obviously need to replace the entire can. I am not aware of a way to be able to differentiate between a damaged can and bad white valve without going through the process of turning water off and replacing white valve and then turning it back on to see if it works.