About Backflow


The reversal of flow other than that normally intended. The flow of water or other liquids, mixtures or substances into the distributing pipes of a potable supply of water from any source or sources other than its intended source.


  • Backflow usually occurs when water in property pipes flow back into public water mains through either backsiphonage or backpressure.



The reversal of flow due to sub atmospheric pressure.

  • Back-Siphonage happens when the pressure that is in the water main drops suddenly. This is sometimes due to a main break, along with water in the customer’s pipes that is sucked back into the main water supply.



Any elevation of pressure in the downstream piping system above the supply pressure at the point of consideration, which would cause, or tend to cause, a reversal of the normal direction of flow. This occurs when the water pressure in the water lines are higher than the pressure in the water supply system and water is then pushed back into the main water supply.


  • ​ Backpressure most generally happens in places like highrise buildings that use pumps to increase water pressure so that they can boost the water up to the higher floors.


Cross Connection-

A physical or potential connection or arrangement between two otherwise separate piping systems, one of which contains potable water and the other water of questionable or unknown safety. This occurs when the water pipe to the property is connected to, or in contact with, something other than potable water. During a backflow condition any substance that may be in contact with the water supply that is within the property piping could be drawn back into the water distribution system. This could contaminate the main water supply if the pipe is connected to any industrial chemical, gas, or waste material.


  • Cross Connections typically happen when hoses are submerged in places such as buckets, tubs, or sinks, or attached to waterbeds or spray containers.