Unidirectional Flushing (UDF)

What is UDF?

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UDF is a strategically coordinated effort to resolve discolored water issues. Specific valves are closed in a particular sequence to force dechlorinated water to flush from designated fire hydrants. By directing the flow to only certain hydrants, we create higher water velocity to help clear several miles of water mains.

Why is UDF performed?

WSSC Water performs UDF to clear up discolored water issues.

What causes discolored water?

Discolored water is caused by mineral deposits in the pipes. Discolored water is not aesthetically pleasing, but it is safe to drink. However, we fully realized our customers deserve better. When we do receive discolored water complaints unresolved by traditional flushing (simply opening a hydrant in the area of the complaint), we create a unidirectional flushing program for the impacted area.

How will UDF impact customers?

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Customers could experience discolored water during and after the flushing has occurred. Running the cold water lines in your home or business after the flushing is complete usually clears up any discoloration. Follow these steps to flush your COLD water lines:

• Run all cold water taps for about five minutes or until the water runs clear.
• Begin with the lowest faucet in your home or business and then open the other faucets one at a time, moving from your lowest floor to your highest.
• Once the water runs clear, usually in fewer than five minutes, turn off your faucets in the same order, lowest to highest.
• You should also flush your refrigerator's water lines.
• If the water does not clear up after five minutes, please call us at 301-206-4002.

Will I see a lot of water while the UDF is taking place?

Yes, you will see a significant amount of dechlorinated water flowing from fire hydrants for as long as a few hours at a time.

Can I use my water during this time?

If possible, do not use your water while flushing is happening. If you must, first run cold water until it is clear to remove any particles from your system. You may also experience low water pressure while we are flushing. Your pressure will return to normal once our flushing has ended. 

Is this a waste of water?

While it may appear to be wasteful, flushing is the most effective way to keep our drinking water safe, clean and pleasant tasting. Crews conducting the flushing keep careful records of the amount of water flushed through the lines. Therefore, this water is accounted for and tracked along with other uses of water. This is a preventative maintenance program, so a little planned flushing now can save a lot of unplanned flushing later.  And in some instances, the water is returned to the aquifer, rivers or streams from which it was withdrawn as groundwater recharge or surface water runoff.

Who pays for the water?

Just like our other maintenance programs, funds from utility rates pay for this program. The water used for flushing is then paid for through water rates since it is factored in as non-revenue water in maintenance expenses. Uni-directional flushing is expected to use less water overall than past flushing efforts.

Water is essential to our daily lives, and we understand the inconvenience these types of projects can cause. WSSC Water appreciates your patience as we work to provide safe, seamless and satisfying water services to your home.