I need to shut off my pool Autofill valve to determine where I may have a leak. I'm getting a lot of water from my overflow and backwash drain and trying to diagnos the problem. Except I can't figure out how to shut down my autofill. Its connected to my sprinkler system and I thought if I just turned my sprinkler system off that should do it but it didn't. I seem to find a shut off valve. I attached a picture of it here. Any ideas?