What is Backflow and Back-Siphonage?
As we will learn in the video from Brian Morrison from the Public Works Commission in Fayetteville, North Carolina there are two types of backflow: back pressure and back-siphonage.
Back Pressure is any pressure that works against the pressure generated by the water supplier. A back pressure occurs non potable water pressure is greater than potable water pressure. Higher water pressure can be due to elevation differences, high pressure booster pumps, boilers which create high temperatures and pressures.
Back-Siphonage occurs when the supply line pressure falls below atmospheric pressure (14.7 psi at sea level). When atmospheric pressure is greater than the potable water side then a reversal of flow can take place from the non potable side. Backflow can happen during that differential pressure and a cross-connection provides the link between potable water and non potable source.
High water demand can reduce potable water pressure from the water purveyor when it exceeds the amount being supplied. An example of high water demand can be fire fighting, water line flushing or breaks in the water main.
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