Over time general usage can cause riser seals to wear out, similar to the wiper blades on a car, they require replacement. The signs of this are usually heads that have riser stems stuck up after the operation, or excessive leaking around the riser seal while the head is in operation. Fortunately, replacement is simple and riser seals are generally inexpensive.
To illustrate the ease of this installation, we've chosen to use the Hunter Pro-Spray 4" model with a 10 ft (3.0m) Pro-Spray Fixed nozzle.
Unscrew the head's body cap counterclockwise to allow access to the riser seal.
After the body cap is removed, you can then remove the internal assembly. The nozzle will keep the riser seal and spring in place until removed.
With the spring's tension pushed down, unscrew the nozzle counterclockwise. This assembly will be under pressure so be sure not to lose the spring.
Remove the old riser seal, replace it with the new wiper seal. (P/N 472300)
Hold down the spring to make nozzle installation a little easier and release.
Once the internal assembly is reconstructed, it can now be reinstalled into the spray body.
Note: If this procedure is attempted with the spray body still in the ground, be sure that no debris gets back into the lateral lines. If this does happen, thorough flushing will need to ensure before the internal assembly is reinstalled.
Hand tighten the body cap by turning clockwise and test the system.