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Backflow FAQ Definitions

What is backflow?

When the water in pipes goes in the opposite direction from its intended direction of flow, a problematic condition called “backflow” occurs. Springfield Utility Board (SUB) controls water quality up to the point of the water meter. After this point, water quality can be degraded or contaminated within a private property plumbing system. When backflow occurs, water from inside a private plumbing system can be pushed back (backpressure) or pulled back (back siphonage) into the community’s drinking water supply. On a smaller scale, backflow can be isolated within a single property when water from a source, like a sprinkler system, pushes or pulls the water back into the property’s drinking water supply.

There are two situations that can cause the water to go backward (backflow):

  • Backpressure – the water pressure in your pipes is greater than the pressure of water entering your pipes.
  • Backsiphonage – a negative pressure (vacuum or partial vacuum) in one of the pipes. This situation is similar in effect to the sipping of water through a straw.
    Backflow prevention assemblies are used to help prevent backpressure and/or back-siphonage.
What is a cross-connection?

A cross-connection occurs when a pipe designed to carry safe drinking water is connected at some point to a pipe containing unsafe water or other liquid material. You may not think of your home as having such hazards, but if you have a hose that is submerged in a pool, carwash bucket, bathtub, or laundry sink, or if you have a pesticide sprayer connected to a garden hose, you’ve created a cross-connection. If a water main breaks, the potential exists for unsafe substances to be siphoned back into the water supply. This means that contaminated water in a pool, carwash bucket, laundry sink, or pesticide sprayer could be drawn into the water system. Once there, the contamination could affect many.

What is a backflow assembly?

A backflow assembly (also known as a backflow preventer) is mechanical plumbing equipment that is installed on your domestic plumbing service. Once installed and tested, rubber checks and springs inside of the backflow assembly will prevent any water from flowing in the reverse direction. Backflow assemblies must be tested annually.

All backflow assemblies must be both State approved, which are assemblies accepted and listed as approved by the University of Southern California Foundation for Cross Connection Research.