If dirt or debris has clogged a sprinkler head, causing it to spray unevenly or not at all, you will need to clean it. First turn off the sprinkler and then do the following:

1) First try a quick, simple cleaning--just try to clear the head's water slit or hole with a piece of small-diameter, stiff wire or a knife blade.

2) For hard-to-clean heads and other certain types, unscrew the head and check for a small filter screen. Flush the screen and/or the head with running water.

3) If the problem is with a pop-up brass head, clean any debris away from the wiper seal on the stem. If several heads in a row have this problem, the water pressure may be too low to raise all of the heads properly.

Be sure the sprinkler valve is turned all of the way on. You can also replace the heavy brass heads with lightweight plastic types.