All impact sprinklers work in the same basic fashion. This includes impact style rotors as well as most of the different styles or brands available today. The following is a quick overview of how an impact sprinkler works.
Water enters the bottom of the sprinkler through the bearing nipple, proceeds up through the body and exits out the nozzle. When the water hits the arm, it is propelled out away from the sprinkler. This action causes the arm to pivot away from the water stream, creating tension on the arm spring. When the spring tension is stronger than the force against it, the arm moves quickly toward the water stream and “impacts” against the body. This “impact” causes the sprinkler to turn in a very consistent manner. This is where the term “impact” was derived from.
All Rain Bird Sprinklers share a common trait. This common trait is very important when troubleshooting impact sprinklers!
All Rain Bird Sprinklers Are Water Lubricated
The worst thing that can be done to an impact style sprinkler is to apply a foreign lubricant. This includes oil, WD-40, silicone, Teflon, pipe dope, etc. These foreign lubricants might make the sprinkler work right away, but it will actually cause the sprinkler to wear out faster. Foreign lubricants attract dust and debris. When lubricants are applied to the bearing washers initially, an oil base forms on the washers. This allows the sprinkler to spin freely for a short time only! Over time, dust is attracted to the washers on the bearing stack. This causes additional friction on the washers and causes them to wear out much faster. If foreign lubricants have been applied, all of the washers and seals will need to be replaced. It is also a good idea to clean the brass at this time by a process called bead blasting.
This ability to rebuild an impact is one of its biggest advantages. Impact sprinklers are totally serviceable in the field. If a foreign lubricant has been used, or if the sprinkler is just worn out from years of use, most parts are available and it is totally serviceable! By simply replacing worn parts (usually washers, seals, and springs) the sprinkler will be in operation for several more years of reliable service.
First check for the obvious. Problems such as: turf obstruction dirt or debris in case or nozzle excessive water pressure
broken arms, trips, etc. foreign lubricants inadequate water pressure