I have a problem with one of my 6 zones, all other zones work fine. This zone gets ok pressure at the first 3 three sprinkler heads then the last 3 wont even pop up. i have checked the valve and its ok , i have checked the last three heads and no problems found. I put this sprinkler system in 15 years ago and fix all my own stuff, for the first time i am stumped, please help.... Tim
