What is backpressure backflow?

Backpressure backflow occurs when the downstream side of the piping system is greater than the supply pressure in a public system or customer’s potable water system.  Backpressure can result from an increase in downstream pressure, a reduction in the potable water supply pressure or a combination of both.  Pumps can create increases in downstream pressure; temperature increases in boilers, etc.  Reductions in potable water supply pressure occur whenever the amount of after being used exceeds the amount of water being supplied, such as during waterline flushing, firefighting or breaks in the water mains.