Ray, Nelson sprinklers are about as cheap a piece of junk as you can get. If the people insist on a similar product get a rainbird. much better made and will last longer. Have a client with 10 acre site that has 426 nelson heads on 7 zones. the system is 20 yrs old and almost all the heads stick up. the guys that mows it is constantly dodging the heads. you should see the striping there! I am trying to talk them into getting rotor heads, less mantenance and better coverage. Every place else that had those heads have long been swapped out, thank God!!
Take care of your customers and they will take care of you.