Backpressure is created when the pressure in a non-potable system, such as in a recirculation system containing soap, acid, antifreeze, or in a boiler system exceeds that in the potable water system that provides the make-up water to the system. This pressure can force the potable water to reverse its direction of flow through the cross connection. Non-potable substances can then enter the potable water system.
What is Backflow?
Cities' water distribution system are designed to keep water flowing from the distribution system to you the customer. However, when hydraulic conditions deviate from normal flow conditions, water flow can be reversed or backflow. When this backflow occurs, water can flow from the customer’s system back into the City’s distribution system.