Backflow is the flow of water or other liquid, mixtures or substance into the distribution pipes of a potable water supply from any source other than the intended source. It can result from pressure changes associated with improper cross connections. There are 2 types of backflows: back siphonage and back pressure. There are 3 types of backflow preventers that are testable devices:
Double check valve assembly
Pressure vacuum breaker
Reduced pressure backflow preventer
Before installation of a backflow preventer the customer needs to complete and get approval from the Water Department by submitting a design data sheet. The cost for testing a backflow preventer by the Department is reflected in the Specialty Fees Section (PDF) on the Utility Billing Administration page.
Backflow preventers are installed where the actual or potential connection between a pipe conveying potable water from a public water system and any unapproved non-potable water piping arrangement that are interconnected. The City of Framingham Water Department has a containment policy. This means that all commercial, industrial, institutional, and municipal buildings will have a reduced pressure backflow preventer installed directly after the water meter.