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Starting Monday, May 1, 2023, the Environmental Service will proceed to its annual unidirectional flushing program of the drinking water distribution system. It will be performed from Monday to Friday, between 7 a.m. and 3:30 p.m., for an approximate period of 5 weeks. The flushing program schedule can be found at the end of this notice.

What is unidirectional flushing (UDF)?

Also performed by many other cities, it is a maintenance process used to clean the inside of watermains within the drinking water distribution system.

Its process involves high-velocity water flow – created when directing water flow in one direction and cutting off flows from intersecting pipes.

UDF is considered to be one of the best ways to preserve good drinking water quality in a distribution system. It also provides an opportunity to evaluate the quality of infrastructure, such as street valves and fire hydrants.

How does it work?

  • Watermains are isolated by closing pre-selected street valves in a specific sequence.


  • Creating high-velocity water flow, it lifts and flushes sediments from naturally occurring mineral deposits that have built up in the pipe.


  • Water is flushed through selected fire hydrants, onto streets or other surface areas, until it runs clear.


  • Flow and pressure data from the flushing are collected. Valve or hydrant deficiencies are also noted at the same time.
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Cloudy or discoloured water

When flushing is being done in your area, you may notice a slight drop in water pressure, with or without a cloudy or reddish (rust) coloration of the water. We understand this can be disturbing but please note that this colouration does not pose any risk to your health.

Here are some tips:

  • Always check the colour of the water before use. If possible, activities such as laundry and dishwashing should be done during the evening.
  • If your water is cloudy or coloured, leave the cold-water taps running until the water returns clear. This should not take longer than 5 minutes. If the water doesn’t clear in 5 minutes, wait 30 minutes and try again.
  • Use hot water only when cold water is clear again.
  • If you still experience low pressure or coloured water after 30 minutes, please contact us at (613) 678-9269 or by email at .
  • Outside office hours, if the problem is urgent and cannot wait for the reopening of the offices, contact the Fire Service Dispatch Center at (613) 632-1105.

Unidirectional Flushing Program Schedule

The tentative flushing program schedule is available below. Commercial, industrial and health care establishments that would like to receive an advance notice of flushing dates in their specific location are invited to contact the Environmental Service at (613) 678-9269.

Please note that, while we do our best to provide accurate information, we cannot determine an exact date or time we will be in your area. The schedule can be subject to change based on weather, road, traffic, and other conditions that are beyond our control.

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We thank you for your understanding and your collaboration during this period and we apologize for the inconvenience related to this operation that is necessary to maintain the quality of our drinking water distribution system.