Example of Reversal of Flow – Backflow Backpressure Case 1

The boiler feed line is directly connected to the boiler for safety measure and for filling the system. No backflow prevention device is provided but a valve separates the two systems. Chemicals are added to the boiler water to treat for scale prevention and corrosion control.

The boiler water recirculation pump discharge pressure exceeds the pressure of the public water system service line. Because the boiler is creating a backpressure situation chemically treated boiler water is being pumped into the potable water system through the opened or leaking valve located between the two systems. Individuals consuming water within the building will be consuming boiler makeup water.

A backflow prevention device shall be installed on the boiler makeup water line.