Question
recently I returned home from work on a day where my sprinkler system was not even supposed to run to find one head running at aproxamatly 1/6th pressure.  Everything else was not running.  I shut off the water to the system and after quite some time it stopped.  the next day I bought a replace ment head and tried it out with the same results.  All the other heads work as they normally should except this one it will keep drizzing water until I shut it off in the ground.  There are multiple heads in the same zone that shut off normally in order to help with the troubleshooting.  Any ideas what could be causing this?

Answer
Hey Mark, I hope this helps. Is the head that is leaking, the lowest head on that zone? More than likely, the automatic valve for this zone, is probably not shutting off all the way, and is leaking water all the time. It's like having a leaky faucet, except in your case the valve is leaking a little bit of water, and it is showing up at the lowest head. What you would need to do is find your automatic valve that runs this zone, and either replace it or re-build it. Usually when you find the valve, listen to it, and see if you hear water running through it, indicating that the valve is not shutting off all the way. A good website to give advice and show you how to re-build or replace a valve is: www.irrigationtutorials.com. Let me know if I can be of anymore help, thanks and have a great day.