When irrigation sprinklers are originally laid out and installed, they are flush with the top of the sod. However, as time progresses and the grass thickens, it can impede the water flow from the sprinkler. This is the time to put a riser on the sprinkler. Risers can be as short as an inch, and as long as 24 inches. They are designed to raise your sprinkler body so that it is once again flush with the top of the sod. You can easily install risers on the sprinklers that require them.
Turn on the irrigation, and place flags by all the heads whose flow is impeded by grass. Turn off the irrigation.
Using a trowel, gently remove the sod surrounding one of the flagged sprinklers. Place the sod and any dirt on a piece of cardboard so it can be easily put back in place when the job is complete.
Clear any excess dirt away from the base of the sprinkler. Unscrew the sprinkler from the PVC pipe.
Select a riser with a length that will raise the sprinkler head up to the surface of the sod. Screw one end of the riser into the PVC pipe until it is snug.
Screw the sprinkler onto the other end of the riser. If the sprinkler is no longer facing in the correct direction, unscrew the top section and pull it out. Decide which way the sprinkler needs to face, and insert the top section back into the body so that it is now facing the correct way. Screw the top section back onto the body.
Replace the soil and sod around the sprinkler.
Continue with this procedure for all flagged sprinklers. When complete, turn on the water and make certain all sprinklers clear the top of the sod, and that water flow is no longer impeded.