Unidirectional flushing (UDF) improves water quality and pipe capacity

Maintaining excellent water quality in a distribution system can be a daunting task. While there is no one-size-fits all solution to maintain or improve water quality, one method gaining popularity throughout the nation is unidirectional flushing, or UDF.

The goal of UDF is to deliberately flush water through distribution system pipes at a high velocity, creating a scouring action that washes away debris, color, and stale water. This is accomplished by closing valves and opening hydrants in a particular sequence so that water is flushed through a hydrant from one direction. Conventional flushing, by contrast, takes less planning but results in lower velocities and less scouring. UDF benefits the distribution system in many ways:

  • Sedimentation and biofouling (which naturally build up in the distribution system over time) are removed before they become a problem
  • Taste and odor concerns are addressed by refreshing stale water
  • Flow capacity is maintained or improved
  • Chlorine residuals are maintained or restored
  • Hydrants and valves are exercised
  • Operator knowledge of the system is improved
  • Water is used efficiently
  • In irrigation systems, foreign objects such as snails or clams can be removed

Over several years, and with the input of operators from multiple water systems, HAL has developed custom computer tools to design UDF sequences. These tools have been used to help water systems across the Intermountain West implement effective UDF programs that have conserved water (as compared to conventional flushing programs), reduced customer complaints, and enhanced water system performance. Operators have praised HAL’s UDF plans for their time efficiency, water efficiency, ease of implementation, and low customer impact.

If you would like to discuss a UDF plan for your water system, contact Ridley Griggs, P.E., at info@hansenallenluce.com.

Photo courtesy of Suez Water Idaho.

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