The State of Minnesota requires backflow preventer assemblies on all in-ground
irrigation systems. The testing of all irrigation system backflow preventer devices must be
completed each year, preferably at the time of the system start-up.
Shakopee Utilities requires all backflow device be tested annually, which is quite smart as the older ones have more failures.
State law only requires testing of units installed after January 23, 2016.
This isn't national plumbing code nor recommened by the manufactures of backflow devices. Annual testing should be for all testible backflow devices, this could open city and water suppliers to legal issues and possible insurance coverage issues, because once the water leaves there water plant. They have no idea if it may become contaminated down stream and by testing it could have been prevented by having working backflow prevention devices.