Sprinkler Head (Aches)

This has been the story of my spring - leaking sprinkler heads! I can't count how many we have replaced this year and every time I turn around there is another one! My sprinkler expert suspects it is caused by a plumber that installed an overflow valve at the property line last fall and didn't properly flush the system when he was done, resulting in lots of dirt and debris making it to the sprinkler heads and clogging them up. In Southern California we rely on our underground sprinklers to keep everything alive, especially in dry years like this one. I am hoping we won't have anymore problems because I think we have had to replace almost every head so far!