Backflow prevention devices are required on all domestic and irrigation water supplies. These devices ensure that contaminated water does not flow back into the water system in case of a power outage. Backflow devices on irrigation systems should be certified every five years by a plumber who has been certified for these tests. This is to ensure that the device is working correctly. Results from the test should be faxed to 734.944.1103 or emailed to email@example.com.