What is Backflow Prevention?
Backflow is the reverse flow of undesirable materials and contaminants into the water mains. Backflow can happen because of two conditions: backpressure and backsiphonage.
Backpressure occurs when pressure in a pipe connected to a main pipe in the distribution system becomes greater than the pressure in the main pipe itself. When this happens, a net force acts on the volume of liquid in the connecting pipe, allowing unwanted material to enter the main pipe. A good example of backpressure is when a pump is involved somewhere in the system creating higher pressure than the city is delivering.
Backsiphonage refers to a situation where the pressure in a service pipe is less than the atmospheric pressure. If water in a supply line is turned off, such as when a pump fails, backsiphonage can cause contamination to be sucked into the system due to a vacuum in the service line. A good example is when a city water main breaks. Instead of pumping water to your location, it is now siphoning water from your location, thus pulling any pollutants or contaminants into the city supply and thereby creating a hazardous situation for the community.
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