I have a zone with Rainbird 1800 pop ups. Recently I noticed the lawn on the lower end was like a swamp. I realized I had a leak. No, that's not the dumb part. I figured out that the leak was coming from around an 1800 on the upper end of the lawn. So, here it comes, I got my shovel and a towel and dug it out. Had to wait for my wife to come home from a short trip before I could turn the zone on and see where the water was coming from as when I tried it alone, by the time I got from my controller to the trouble spot, the hole was filled with water. So, I took the 1800 off and capped the line. Then watched as the wife turned the water on. Guess what! No leak. So now I begin to smarten up. I inspected the 1800 and found the cap was just barely hanging on. Water obviously had been leaking from there and not a broken pipe. Replaced the head with the cap securely tightened and sure enough, no leak. I did end up with a new head because the original was very old and was not sealing around the pop up too well. Sure could have saved some digging in 100 degree heat if I had checked the cap first! Morale of the story? Test don't guess.