System Flushing


Components of a Distribution System Unidirectional Flushign Program



Aging/Decaying Pipes






Why You Might Need a Flushing Program

In General In Particular

To Remove Impurities

  • accumulated
  • associated with new and repaired mains
  • associated with complaints
  • hazardous to the public health


  • Reduce
    • high bacterial concentrations
    • chemical contamination
    • turbidity
  • Remove
    • tastes and odors
    • discolored water
    • accumulated sediment
  • Respond to customer complaints
  • Increase chlorine residuals
  • Increase/maintain the life of mains



Flushing Strategies


Spot Flushing Reactive. Most common type of flushing. Used when there are local quality complaints
Stagnant Area Flushing Short term preventive. Used in areas with longer detention times (i.e. Dead-ends, low demand areas)
System-wide Flushing Long term preventive. Most comprehensive form of flushing. Maintains WQ and useful life of the mains.




Flushing Methods



Conventional Flushing

  • Water from all directions
  • Low flow velocities
  • Less scouring
  • Don't control flushing direction





Unidirectional Flushing

  • Water channeled
  • Higher flow velocities
  • More scouring/better cleaning
  • Systematic valve operation





Continuous Blow-off

  • Water "bled" at stagnant areas
  • Low flow velocities (< 1 fps)
  • Less scouring/poor cleaning
  • Large quantities of water used





"Traditional" Flushing






Unidirectional: Deciding When and Where to Flush

When: Time


Where: Location



What Data Will You Need?



Data Directly Related to Flushing Program



Data Indirectly Related to Flushing Program



Background Information Requirements



Do Not:




How Flushing Works (In The Field)



How Flushing Works (Program Administration)

Refinement/Redirection of Basis for Decision to Flush

Design Considerations When Extending the Distribution System

Program Champion




Elements of Unidirectional Flushing Program

The following elements go in a continuous cycle:




The Flush Program Coordinator is responsible for:


The Flushing Crew is responsible for:


The Routining Crew is responsible for:



Why Use a Hydraulic Model?

Models are extremely valuable tools for planning, engineering and ops

"One size doesn't fit all" - each hydraulic system has unique characteristics, and there are different platforms available

Today's software is extremely sophisticated, and user friendly, but.....


The "Modeling Bar is Raising"


Models Migrating to GIS Interface

Distribution System Models are important tools now, but are only going to become more important



What are Benefits of Hydraulic System Modeling?



Creating a Hydraulic Model

Infrastructure: All Physical Facilities in System








Data Used in Hydraulic Modeling