Water main flushing

Have you ever seen water flowing from a fire hydrant, but not a fire in sight? You were probably watching a water main being cleaned using a flushing process. Water main flushing is widely used by municipalities to effectively clean pipes, water mains and water distribution systems to deliver safe drinking water to customers.

When water main flushing typically occurs

Water main flushing can be planned as part of regular system maintenance, or when we drain or commission existing water mains. It can also be unplanned, such as after water main breaks, infrastructure damage or infrastructure failure.

For planned work, EPCOR crews typically work during the day from January through March. They try to avoid working around dinner during the peak flushing period. To learn what we are doing and how long we will be in your neighbourhood, check the water main flushing schedule posted in customer notices.

How to know if water main flushing is occurring in your neighbourhood

If you see an EPCOR vehicle and/or water flowing from a hydrant
You may experience temporary low water pressure or cloudy water while we are flushing fire hydrants near you

If you experience sudden low water pressure that isn't due to water main flushing, you can follow our guide to troubleshoot for low water pressure in your home.

Important: Don't use any type of liquid lawn products that attach directly to your hose when your area is receiving UDF service. Due to the water pressure change, anything attached to your hose could be sucked into it and will end up in your water main, potentially contaminating your and your neighbours' water supply. You can learn more about this hazard on our preventing backflow page.

What to know when we are flushing in your neighbourhood

You may have temporarily cloudy water or low water pressure while fire hydrants near you are being flushed
Your water won't be turned off, and you'll continue to receive uninterrupted water service to your home
Water main flushing can take anywhere from 15 to 60 minutes per fire hydrant to complete, with an average of approximately 25 minutes per hydrant. You may experience temporary low water pressure or cloudy water during this time
Water main servicing doesn't affect your water bill. You're only charged for water that passes through your meter, and flushed water is emptied out of the distribution system well before then

Water main flushing using UDF

Unidirectional flushing (UDF) is the water main cleaning method EPCOR uses for our flushing of water mains procedure. UDF simply means guiding water in a single direction through the pipes by systematically closing valves and releasing the water through fire hydrants.

Most utilities use some form of flushing and disinfection of water mains in their regular maintenance schedule by opening a hydrant in the distribution system and flushing for an extended period of time to move water. The process is known as traditional flushing. Although lots of water is moved, this is not a very effective means for cleaning inside the water mains, as the water moves from multiple directions at a slower velocity.

UDF, on the other hand, involves the systematic closing of valves and opening of hydrants to create a single direction of flow in flushing sequences. All that water flowing in one direction results in faster velocity and more turbulent flow, which means cleaner water mains and a more efficient water system.

We flush from largest mains to smallest mains, and the cleanest mains to dirtier mains. This ensures dirty water is not being pushed into clean pipes and that the pressure stays high.

Cleaning water mains and flushing hydrants is a necessary part of maintaining a safe and reliable drinking water supply and system. Flushing water lines helps to maintain and improve water quality.

Water main flushing helps:

Scour (scrub) the inside of the pipe,
Remove sediment, silt, and biofilm,
Improve water colour,
Improve turbidity (for clearer, less cloudy water),
Increase chlorine residual,
Reduce flushing frequency and water use, resulting in savings over traditional flushing, and

By pumping high-pressured water through the pipes and releasing it through fire hydrants, biological and mineral deposits are removed from water mains to get the cleanest, clearest water to you.

Because Unidirectional Flushing is more effective at getting the pipes clean, we're able to flush less often. And because the pressure and velocity used in UDF is so much higher than traditional flushing, we actually run the water for a shorter duration. Our flushing schedule is also designed to ensure that we never unnecessarily flush an area.

Any water that is discharged is returned back to the river through our storm systems. To that end, the water is returned to the water cycle.

Water main flushing

Water main flushing

When water main flushing typically occurs

How to know if water main flushing is occurring in your neighbourhood​​

What to know when we are flushing in your neighbourhood

Water main flushing usin​g UDF

How to know if water main flushing is occurring in your neighbourhood

Water main flushing using UDF