I have a Febco backflow valve that has started leaking under the bonnet, only when zone 4 of my 7 zone sprinkler system starts. The whole valve is only 2 years old and the rest of the system is 5. The leak will only last a couple seconds, but dumps quite a bit of water before it reseals itself. I have not taken apart the Febco yet to see if the pieces are cracking or the o-ring is cracked. I would think those should be fine if it is only leaking on one particular zone. Any ideas what could cause this issue?
I should note that contacting the installing company is not possible because they went out of business right after finishing my system.