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Improve Water Quality with a Solid Unidirectional Flushing Program

Dan Calano
Jun 8, 2021 11:53:00 AM


Unidirectional Flushing (UDF) is an excellent method of cleaning water distribution pipes in order to improve water quality and operations, improve service standards, and restore capacity.

A successful UDF program will maximize the benefits of your asset management program for years to come. Here is everything you need to know about unidirectional flushing and how to create a successful UDF program with long-term benefits.

Unidirectional flushing vs. conventional flushing

Water mains need to be flushed to extend their useful life, and one way to do that is through flushing. Water main flushing is an effective method to remove unwanted tastes, odors or discolorations of the water, and it improves chlorine residual.

Flushing programs are typically complex for field crews to coordinate. They require collaboration from a long list of stakeholders that include departments, agencies and customers. They also work across the network with process disruptions and need timely cooperation from multiple crews.

UDF field activities are very similar to conventional flushing. One major difference between the two is the opening and closing of valves after each flush.

Conventional flushing

Conventional flushing consists of opening hydrants in different areas and discharging the water until accumulations are removed and the water becomes clear. Although easy for maintenance crews, this method requires a large amount of water and may not completely clean the entire pipe network.

Unidirectional flushing

Unidirectional flushing is a more effective way of cleaning than conventional flushing and uses an average of about 40% less water. UDF isolates each pipeline to create flow in a single direction to quickly and efficiently clean the pipe network.

By concentrating flow into the pipes, UDF creates higher velocities that are better able to clean, meaning the sediment, corrosion products and biofilm are flushed out and not just moved to another pipe - which is often the case in conventional flushing. Cleaned pipes from UDF may have improved water clarity or color, reduced turbidity, and improved chlorine residual.

Unidirectional flushing programs

A UDF program should be well planned in order to help establish safe conditions for maintenance and operation crews and the public, as well as maintain outstanding service to customers.

5 benefits of a unidirectional flushing program

A unidirectional flushing program is a best practice for asset management that cleans and maintains your community’s water distribution piping. A successful UDF plan offers 5 long-term benefits for your utility.

1. Improves water quality

UDF programs and regular sequenced flushing helps improve water quality. Communities are able to maintain their water supply systems and schedule routine water main and fire hydrant flushing, which removes sediments, deposits, and biofilm buildup from water systems. This improves overall water quality.

It is important to note that if not done properly, UDF can move water fast enough to stir up sediment instead of removing it, which is why UDF programs are crucial.

2. Improves the capacity of existing pipes

UDF is an effective method for cleaning and flushing out pipes, which greatly improves their capacity. More specifically, unidirectional flushing ensures that the system is flushed with clean source water and that high flushing velocities are achieved. This helps reduce sediment, biofilm, and corrosion products, which improves operation of the water system and allows field crews to identify inoperable valves and hydrants.

3. Decreases frequency of flushing

Unidirectional flushing creates higher velocities that are better able to clean the pipe, which ultimately decreases the frequency of flushing. Flushing is performed in a set sequence to make sure a clean water source is always used and it is done properly.

Ex: Flushing by opening a hydrant may create a flow of 2 feet/second in the water main. However, by systematically closing valves with UDF, the flow will often reach 6 to 8 feet/second. This ensures more effective cleaning and less frequent flushing.

4. Can use less water than conventional flushing operations

As stated above, UDF uses 40% less water than conventional flushing methods. By using less water, unidirectional flushing is more efficient when it comes to water use and could be a part of a water conservation program.

5. Reduces customer complaints

Discolorations, tastes and odors from the water pipeline during the cleaning and flushing sequences can be alarming to some customers. During flushing activities, flushing crews and customer service staff are likely to receive customer concerns and questions.

However, a solid and successful UDF plan reduces the number of customer complaints, as it improves the communication of flushing to the public and improves the flushing and cleaning of pipes altogether.

5 steps to creating a UDF plan

A UDF plan is essential to ongoing, effective utility asset management. When creating a unidirectional flushing plan, it’s important to ensure that your business system assets are complete and accurate.

  1. Document assets - Complete and accurate information allows field crews to execute flushing sequences without failures from inadequate system pressures or low flow conditions.
  2. Critically analyze assets - Your physical assets used in the UDF sequences have to work. Unusable control points are omitted in flushing plans.
  3. Create a UDF plan with GIS maps - Your entire service area should be split into flushing zones and those zones subdivided into flushing sequences with detailed maps for each sequence.
  4. Execute your UDF plan - Make sure to notify the public of your upcoming flushing sequences.
  5. Measure results - Collect flow and pressure data from the flushing sequences as they are being completed.

UDF is a no-brainer - we are here to get you over the hump. Improve your water quality, manage your assets, and plan your capital spend in a smarter way. Find out how Utility Cloud can help manage and report on your hydrant flushing and maintenance program from one screen.

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