Flushing Tips: Implementing a Unidirectional Flushing Program

How to Implement a Unidirectional Flushing Program and Improve Your Efficiency, Conservation

By Lara Kammereck & Dan Reisinger

Unidirectional Water Main Flushing (UDF) is increasingly used across North America to improve operations, enhance the water system and improve service standards. Water main flushing has long been considered an effective method to remove unwanted tastes, odors or discolorations of the water, and to improve chlorine residual. UDF, a specific type of water main flushing, provides greater cleaning and uses less water than conventional flushing. This article focuses on the implementation of a UDF program, and implementation considerations are discussed for program planning and field activities.

Conventional Flushing

The conventional flushing method consists of opening hydrants in the different targeted areas and discharging the water until the accumulations are removed and the water becomes clear. This method of flushing is easy to conduct by maintenance and operations crews, but requires a large amount of water and may not completely clean the pipe network. The graphic in Figure 1 shows how the water flows to an open hydrant, using the conventional flushing method. The water moves freely from all directions to an open hydrant. Since there is less flow in a given pipe, velocities may be too low to adequately clean, or scour, the pipes.