Clean clogged lawn sprinklers with special cleaners that dissolve rust and mineral build-ups, especially iron, if you have hard water.
Fill a freezer bag half full of CLR or a similar rust remover and drop your sprinkler into the bag. Swish it around occasionally to distribute the solution. Remove the sprinkler after 30 minutes and rinse it in clear water.
Spray silicone on the cleaned-up sprinkler to lubricate the parts and to prevent iron and mineral buildup.
If you have a lot of iron or other minerals in your water, then you know the problem. Iron builds up on the working parts and in the holes of sprinklers. Impact sprinklers like the one here can quit working altogether. A simple soaking in a rust-removing solution followed by a spritz of silicone lubricant will rejuvenate your sprinkler. We used CLR Calcium, Lime and Rust Remover, but other rust-removing solutions will also work. Soak the sprinkler for about 30 minutes (Photo 1). Then remove the sprinkler and clean off any remaining mineral or rust buildup with a brass-bristle brush.