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Unidirectional Flushing Program

Cleaning the inside of water lines supports and maintains an effective water distribution system and helps ensure high-quality water is delivered straight to your tap. The best way to clean the inside of water lines is by harnessing the power of the water itself. The Clayton County Water Authority is piloting a standard industry practice known as Unidirectional Flushing (UDF) to clean its system.

UDF basically isolates a segment of pipe by closing off valves and opening hydrants to direct clean water down a single water main. The water pressure creates enough velocity to scour the pipe and remove any sediments from the bottom of the pipe. It’s like using a pressure washer to clean a home or sidewalk. UDF provides greater cleaning and uses less water than conventional flushing.

The general objective of UDF is to assist in preserving and/or improving water quality and service.

CCWA relies on its UDF Program to:

  • Improve water quality
  • Improve carrying capacity of pipes
  • Benefit the operation of the water system

A UDF plan identifies the general sequence of pipes to be flushed, which valves will be closed and when and how long each flushing sequence is expected to last.

Flushing the water distribution system, which serves homes and businesses, can help address a variety of water quality concerns such as taste and odor, discoloration, and sediment in the water. The photo shows a water line after UDF.


Frequently Asked Questions Regarding Unidirectional Flushing 
What is ‘unidirectional flushing’?

Unidirectional flushing (UDF) is a standard industry maintenance practice used to scour, clean, and improve the carrying capacity of our water distribution system. Unidirectional refers to the fact that during the cleaning, water is only flowing in one direction. This type of maintenance helps us continue to provide our high-quality drinking water to our customers.

CCWA’s water distribution system is set up in a grid-like pattern which allows water to be fed from several directions at the same time. When performing unidirectional flushing, CCWA’s crew will open and close pre-determined valves to isolate a specific section of water main.  They then open a specific fire hydrant to draw water through and flush the now-isolated section of water main. The speed of the water flowing through the isolated section of main is greatly increased, producing a scouring effect.

The scouring effect removes any potential sediment buildup and cleans the water main. Test samples are collected from the water flow exiting the hydrant. The samples are then tested to determine the turbidity (clarity) of the water. The duration of each unidirectional flushing sequence is determined by the turbidity of the test samples. Once samples show turbidity at or below the targeted level, the hydrant will be closed and the process is complete. 

How will I know when unidirectional flushing will be taking place in my neighborhood?

CCWA crews will place notification signs on the commonly traveled streets near where flushing will be taking place. Please be aware that there is no way we can determine an exact date/time for when we will be by your location. Please regularly check our website and follow us on Facebook for updates regarding the progress of our flushing program.

I am a water-sensitive customer, how can I make sure my service is uninterrupted?

We realize that some of our customers are water-sensitive for a variety of reasons (businesses, medical concerns, etc..). Although we strive to provide continuous service to our customers, there may be brief durations of low water pressure for customers adjacent to where we are performing the unidirectional flushing. If you have concerns about maintaining continuous water service, please contact our Call Center at 770.960.5200. We cannot guarantee uninterrupted service, but we can coordinate with you directly to keep any interruptions to a minimum.

What should I expect when unidirectional flushing is happening in my neighborhood?

Customers in the immediate vicinity of where flushing is taking place may experience a temporary drop in water pressure. If this does occur, please be aware that CCWA staff is diligently working to minimize any inconvenience caused to you by our flushing process. Flushing typically Monday – Friday during the day. Our crews will not have heavy equipment out during cleaning.

How long does it take to flush each water main?

Our experience has ranged from 20 minutes to an hour or possibly longer and is dependent on a variety of factors. Factors include the age of the water main, the type of pipe, the length/diameter of the water main being flushed, and if any sediment buildup is present. The time is ultimately determined by the turbidity (clarity) of the water being flushed. Test samples are collected from the water as it exits the flowing hydrant. The samples are then tested to determine the turbidity of the water. Once the test samples show turbidity at or below the targeted level, the hydrant will be closed, and the process is complete.

Can I use my water when flushing is taking place?

Yes, you can use the water while we are flushing on your street. Please be aware, however, that our flushing process may stir up rust particles and sediment that may have accumulated over time in the water main. If you use water while we are flushing you may notice discolored water. You may also experience low water pressure while we are flushing. If this happens, your water pressure will return to normal once our flushing has ended.

Is unidirectional flushing a waste of water?

Unidirectional flushing is not a waste of water. CCWA has five raw water reservoirs. The water used during our unidirectional flushing program drains into our stormwater system and eventually makes its way back to our reservoirs through local creeks and streams. 

How will the water being used be paid for?

Funds from CCWA water and sewer rates pay for this program, just like all other CCWA maintenance programs. Water rates will not be increased to pay for unidirectional flushing. Each residence and business is individually metered to determine each customer’s individual usage. Your utility bill is based on your specific meter readings.

Who do I call with additional questions?

You may call us at 770.960.5200 with any questions you may have.