Backflow inspections are performed by backflow technicians who connect test kits into the device's test ports. These test kits verify that the flow of water is moving in the correct direction. Depending on the placement of the backflow device, tests can be performed outside the home without owner supervision. If the device is located indoors, the homeowner must be present during testing.
Yearly inspections of backflow devices are required because they can fail at any time and cause the flow of water to reverse. This reversal could potentially contaminate a shared drinking water supply with solids, gases, liquids or a mixture of the three. Approximately 5 percent of backflow inspections result in failure. Common causes for failure include broken springs, torn seals or work O-rings. Freezing temperatures can cause cracks in castings and poppets.
A backflow device can be worn down by the quality of the local water, usage frequency, where it was installed or the building's water pressure. Some issues may be noticeable by the homeowner, such as water leaking from a relief port. While infrequent drips are normal, constant leaking is not, and a backflow technician should be contacted as soon as possible, even if inspection is not due.