Turn the water on to your entire sprinkler system. Rotate the main control knob counterclockwise with your hand until water spurts from all of the working sprinkler heads.
Take note of the location of working sprinkler heads. The suspected non-working head should be close or possibly in line with other working sprinkler heads. There will be an unusually large gap between heads where the buried head is located.
Turn off the water to the sprinkler system by rotating the main control knob clockwise with your hand until the water no longer spurts from the sprinkler heads.
Measure the distance between the two working sprinkler heads with the unusually wide gap between them. Note this measurement as this is what is needed to determine the location of the buried head in the large gap.
Measure the distance from the working head next to the buried head toward the location of the next working head. Measure to the distance that was noted in the previous step. This will lead you to the location of the buried head.
Clear away the dirt covering the buried head with a small shovel.
Turn on the sprinkler system by rotating the knob of the main control counterclockwise with your hand.
Take note of any large gaps in the sprinkler system. This can indicate buried sprinkler heads.
Turn off the sprinkler system by turning the main control knob clockwise.
Hover a metal detector over the suspected area containing the buried sprinkler head. A "beep" or message on the metal detector's digital display will indicate the location of a metal sprinkler head and any water lines running to and from the buried sprinkler head.
Remove the dirt covering the sprinkler head using a small shovel.