Unidirectional Watermain Flushing

Water flowing from a pipe next to a fire hydrant.

UniDirectional Flushing (UDF) is a method used to clean and improve the carrying capacity of our water distribution system. This cleaning method helps us continue to provide safe, high-quality drinking water to our customers.

The 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, Utility staff open and close pre-determined valves in order to isolate a specific section of watermain. Staff will then flush this section of main by opening a specifically-selected fire hydrant that will draw water through the now-isolated section of watermain. Since the watermain is isolated and is only being fed from one direction (hence the term ‘unidirectional’), 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 build-up and cleans the watermain.

Test samples are collected from the water as it exits the flowing hydrant. The samples are then immediately tested to determine the turbidity (clarity) of the water. The duration of each unidirectional flushing sequence is determined by the turbidity of these tests. Once the test samples show that the turbidity is at or below the targeted level, the hydrant will be closed and the process is complete.

How will I know if I’m going to be impacted by the Unidirectional Flushing?

MPU flushes different zones every year. To see what zone we’re flushing this summer, check out our map. This map is only updated during the summer.

How will I know when Unidirectional Flushing will be taking place in my neighborhood?

A notification mailer will be sent to all customers serviced in the neighborhoods where we will be performing the unidirectional flushing program.

Each morning crews will place notification signs in the terraces of commonly traveled streets in the vicinity of where flushing will be taking place that day. If you see these signs by your neighborhood, we may be approaching your location soon! Please be aware there is no way we can determine an exact date/time we will be by your location.

I am a water-sensitive customer. How can I make sure my service is uninterrupted?

We realize 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 us at (920) 683-4600. 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?

Unidirectional flushing will have a minimal impact to the majority of our customers. 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 Utility staff is diligently working to minimize any inconvenience caused to you by our flushing process.

During this process, we will be flushing out of fire hydrants onto the road, sometimes causing brief buildups of water on the road. Crews will have the flushing area coned off but it is very difficult to contain all the water. Avoid driving through the flushing areas whenever possible.

Flushing typically occurs Monday through Friday between 7AM and 5PM.

How long does it take to flush each water main?

Flushing typically takes 20 minutes to an hour or possibly longer, depending on a variety of factors, which include the age of the watermain, the type of pipe, the length/diameter of the 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 immediately tested to determine turbidity of the water. Once the test samples show the turbidity is 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?

Our flushing process will stir up rust particles and sediment that may have accumulated over time in the watermain, resulting in discolored water. MPU recommends waiting to use water until our crew has left the area; this would help to ensure that sediment, rust particles and discolored water are not drawn into your home’s plumbing. If you choose to use the water while we are flushing on your street, it is likely that you will draw this sediment and discoloration into your home’s plumbing. You may also experience low water pressure while we are flushing. Your pressure will return to normal once our flushing has ended.

Does Unidirectional Flushing waste water?

Unidirectional flushing does not waste water; in fact, it is more water conscious than regular water main flushing. Our water is drawn directly from Lake Michigan and filtered. The water used during our unidirectional flushing program drains into the City’s storm water system. It then drains into different outfalls that drain into nearby rivers, streams and Lake Michigan – right back where it came from.

How will the water being used be paid for?

Funds from the Utility rates pay for this program, just like any other maintenance program we have. 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 (920) 683-4600 with any questions.


Skip to content