Sprinkler heads on a zone do not completely shut off

If you have a zone where some or all of the sprinkler heads are still trickling water even after the zone is finished its watering cycle, there are a couple of things you need to check.

1. Are the sprinkler head(s) that are leaking located downhill from the zone valve? If so, what may be happening is that the water left in the pipe after the valve is shut off is slowly draining downhill and out of the sprinkler head(s). If this is the case, the water should stop trickling after the water is completely drained out of the zone. If this is a problem for some reason, you can replace the spray heads with the kind that have check valves installed inside of them. The RainBird version is called a SAM (1804-sam, 1806-sam, etc). The check valve keeps the water from leaking out when there is little or no pressure in the line. Check with your local irrigation supply house or, if there is nobody else around, try Lowe's.
2. If your heads are not downhill from the valve and are trickling water even after the zone is shut off, your valve may have issues. The first thing you can try doing is removing the solenoid and looking for dirt or debris in the solenoid. Rinse the solenoid to remove any debris from the plunger (located on the bottom of the solenoid). Also, where the solenoid screws in is a tiny hole. This needs to be unobstructed in order for the valve to work properly. If there is dirt in the tiny hole, use a small paper clip or something to poke it out of the hole. After replacing the solenoid, turn on the zone for about 30 seconds, then turn it off again. If the head(s) are still leaking, you need to next check the diaphragm inside the valve. Do this by removing the cover of the valve and inspecting the diaphragm for holes or debris. If there are holes or it is worn out, the diaphragm will need to be replaced. If there is debris or dirt, the diaphragm needs to be washed and put back into place. If this does not work, replace the valve entirely. You can usually find these parts at your local irrigation supply house, or Lowe's if there is nobody else around.