Backflow in your sprinkler system
Backflow is what happens when water in your sprinkler system flows back in, instead of flowing out, carrying potential contamination from whatever was around the output source. For sprinkler systems, contamination may be fertilizer, pesticides, animal waste or even insects (yes, insects) that can be forced back into a system through a cross connection. A cross connection is where substances other than drinking water may enter the plumbing and come in contact with drinking water. Many cities require that any cross connection have a backflow preventer and to have it tested yearly.