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City of Lincoln
Backflow preventers (also known as backwater orbackflow valves and backflow prevention devices) are installed on sewage pipes to prevent contaminated water from flowing back into a building’s systems or into public drinking water systems during sewage overflow events. Backflow events often occur from flooding or heavy rainfall, but can occur from any sudden fluctuations in water pressure in the public water system, including water main breaks and fire-fighting.
The Uniform State Plumbing Code of Massachusetts mandates backwater preventers for all buildings containing plumbing fixtures located below the manhole cover serving the building. Property owners are responsible for installing and maintaining backflow valves. Annual and semiannual tests and inspections by MassDEP-certified backflow testers are required. There are a number of types of backflow valves approved by the state for different building sizes and types, most of which utilize spring-loaded check valves, as well as other relief and shutoff valves to prevent back pressure backflow and back siphonage. All water lines to the building must have backflow valves, greatly increasing the cost for large commercial buildings.