Watermain Flushing

The City of Port Coquitlam flushes one third of the City’s watermains each year in order to minimize sediment deposits in the City’s water system that can deteriorate our water quality.

Flushing may cause short-term pressure fluctuations along with discolouration and sediment in the water reaching homes and businesses.

At these times, residents and businesses are advised to avoid laundering clothing to minimize staining, and avoid using their hot water system to reduce the amount of sediment drawn into their hot water tank.

When the mains in your area are being flushed, check the colour of your water from a cold-water tap before laundering or using the hot water.

2023 Unidirectional Flushing Program

Our annual Unidirectional Flushing Program is set to start on Monday, Mar. 13, 2023. Flushing will take place in Zone 2, shown in the map, and it is expected to take 6-8 weeks.
Waterman Flushing Map

What should I do if my water is discoloured after you have flushed the watermains?

Water is sometimes discoloured after watermain cleaning, but this should not last long. You should avoid laundering clothing to minimize staining, and using the hot water to avoid drawing sediment into your hot water tank.

To clear your water:

  • Turn on a cold water tap and let the water run for a few minutes. Do not choose a tap that has a water filter connected to it, or the sediment may clog your filter. Do not use a hot water tap because it could draw sediment into your hot water tank.
  • Catch some water in a light-coloured cup or container to see if it is clear. You can use your water if it is clear.
  • If the water doesn’t clear in 5 minutes, wait 30 minutes and try again.

Frequently Asked Questions

What are watermains?

Watermains are underground pipes that carry water from the reservoir to your street.

Why is the City 'flushing' the watermains?

Flushing the watermains improves water quality by removing sediment that slowly build up at the bottom of the watermain over time.

What is uni-directional flushing?

During uni-directional flushing, water system valves are operated to create one-way flow to isolate a section of water main to be cleaned. A hydrant connected to the main is then opened to remove the built-up sediment. This type of flushing increases the speed of the water flow in the main to about two metres or six feet per second (it is normally less than .3 metres or 1 foot per second). This high speed produces a scouring action in the mains, removing sediment deposits. The flushing starts at a clean water source (e.g., the water pumping stations) and moves through the watermain system. This ensures that clean water is always used to flush the mains.

When does uni-directional flushing take place?

Typically early Spring and Fall. We avoid excessive water consumption during the Summer months.

How will I know when the City is cleaning the watermains in my neighbourhood?

The City will inform residents before starting the flushing program by posting notices on our website and placing advertisements in local newspapers. You’ll also see orange signs in neighbourhoods where flushing is taking place.

Flushing may cause short-term pressure fluctuations along with discolouration and sediment in the water reaching your home or business.

Can I use my water when you are flushing the watermains in my neighbourhood?

When you see flushing being carried out on your street, you should avoid using your hot water system to minimize the amount of sediment drawn into your hot water tank.

What if someone accidentally drinks the water when it is discoloured?

Drinking discoloured water should not make you sick, however, it may smell, taste, or look unpleasant.

What else may I notice about my water after you have cleaned the watermains?

Immediately after cleaning, you may notice that your water is cloudy or has a chlorine smell.

Cloudy water
Water is cloudy when air gets in it and makes tiny bubbles. These bubbles are harmless and will disappear if you let the water sit for a few minutes.

Chlorine smell
We add enough chlorine to the water to keep it safe. You can easily get rid of the chlorine taste and smell by filling a container with water and keeping it in the fridge for drinking – much of the chlorine will leave the water overnight.

Does the City monitor the water quality during the watermain flushing program?

The Greater Vancouver Regional District monitors the water quality by sampling and testing at water sampling stations throughout the City on a weekly basis to ensure that the water in the water distribution system is safe to drink.

Are there other benefits to watermain flushing?

In addition to removing more sediment and using less water than conventional flushing, watermain flushing tests and exercises the water system valves and hydrants.

Do other cities have similar watermain cleaning programs?

Many cities have some type of flushing program to clean their watermains (e.g., conventional flushing or unidirectional flushing). This is considered the best way to improve water quality and increase the reliability of the water distribution system.


Tel:  604.927.5496
Emergency After Hours Tel: 604.543.6700
Email  publicworks@portcoquitlam.ca

Location and Mailing Address

Public Works
1737 Broadway Street
Port Coquitlam BC V3C 2M9

7:00 am to 3:30 pm, Monday to Friday (excluding statutory holidays)