Backflow Testing Backflow Prevention Assembly Testing A backflow prevention assembly is a device connected directly to your home or business main water supply where it diverts to a landscape irrigation system. Its operation prevents water from the irrigation system to flow backward into the main city water supply. Backflow devices are an important prevention to the possibility of any lawn chemicals contaminating the main city water supply; regular testing of this device ensures its proper operation. A backflow assembly test takes an average of 15-25 minutes per device. During the test, the main water supply does have to be turned off, but water service will be restored as soon as the testing is complete. (Most residences have only one device, but commercial buildings can have several devices.) Let us know if you need a backflow test, we are pleased to be of assistance.