I have one zone that's leaking whenever the system is running. So, for example, on days where the sprinkler zone in the front yard is running, this zone is leaking out of the downhill sprinkler heads the entire time, sometimes with enough pressure for one of the heads to rise up just a tad.

• First thought was dirt in the valve, so I popped the jar-top valves open, clean the the film and grit off the diaphragm, and checked for any other dirt in there. No effect.

• Next I removed the solenoid and replaced it. No effect.

• Then I switched the upper part of the valve with one from a zone that was working fine. So with that, this zone got a different diaphragm, spring, and solenoid assembly. And the damn thing is still leaking.

That leaves me with no ideas. Is there anything else that could even be broken or dirty in the lower assembly? Any ideas? As always, thanks for your help.