Unidirectional Flushing (UDF) is a standard industry practice used
to scour and clean the watermains. This technique involves a
high-pressure, high-velocity water flow going in a single direction
through a single pipeline. During the UDF process, a section of the
watermain is isolated and water is forced through it at high speed,
then discharged through a fire hydrant. The hydrant is left open
until the water is cleared.