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Water main cleaning program

What are water mains?
Water mains are underground pipes that carry water from the pumping stations to your street.

Why do you clean water mains?
Cleaning the mains helps preserve the very high quality of water as it passes from our new drinking water treatment plant to your taps.

How do you clean the water mains?
We force water through the water mains at a high speed and discharge it through hydrants into sewers. The fast moving water scours sediment from inside the mains. We leave the hydrants open until the water runs clear.

Why do you clean water mains on weekends and holidays?
Our Water Services crews work from 7:00 a.m. to 6:00 p.m., every day of the year except Christmas Day, to get the job done. These staff are not working overtime – they are simply working their regular shift. As well as cleaning the water mains, they repair water main breaks, inspect and maintain fire hydrants and replace water meters.

How long does it take to clean the water mains on each street?
It takes about 30 minutes to 1 hour to flush the water mains on each street.

When do you clean the water mains?
We clean water mains in different areas of the city in spring and summer, seven days a week, from 8 a.m. to 5 p.m. We completed a six-year program in 2008 in which all 2,400 kilometres of water mains were flushed clean in preparation to carry treated water from our new water treatment plant. In 2009, we began our annual water main cleaning maintenance program - cleaning water mains in select neighbourhoods as required during spring and summer.

How will I know when you are cleaning the water mains on my street?
We will tell you before we start cleaning. When we begin, we will place signs at either end of your street that say, "Water Main Cleaning in This Area 8:00 a.m. to 5:00 p.m.".

If you live in a house
We will hand deliver an envelope to your mailbox one or two days before we clean the water mains on your street. The envelope will contain a letter and a brochure with more information on the program. We will place a blue flag in your front yard just before we begin, and we will remove the flag after we have finished cleaning.

If you live in an apartment
We will let your property manager/landlord know, one or two days in advance, when the work will begin and how long it will take. We will leave a package of information, including a fact sheet on the program to hand out to tenants, and notices to post in the building.

If you operate a business
We will contact you one or two days in advance to let you know when the work will begin and how long it will take.

Can I use my water when you are cleaning the water mains on my street?
Do not use your water or flush your toilet when we are cleaning the water mains on your street. Using your water or flushing your toilet could draw sediment into the water pipes in your building, and into water filters, washing machines, hot water tanks, etc. Turn off any time-delayed water systems, such as dishwashers, coffee makers, and lawn sprinklers.

Apartment Landlords/Property Managers and Business Operators
We recommend that you turn off the water supply to the entire building using the water shut-off valve at your water meter (usually found in the mechanical room). This will help prevent sediment from entering the water pipes in your building and getting into your water systems.

Will I notice anything different about my water after you have cleaned the water mains?
Your water may be discoloured. Water is sometimes discoloured after water main cleaning, but this should not last long. Do not use discoloured water for any purposes that require clean water, such as preparing food and beverages, medical and dental procedures, or laundry.

• 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.

Apartment Property Managers/Landlords and Business Operators
Before you turn your water back on to the building, we recommend that you:

• Turn on a cold water tap near the water shut-off valve (e.g., a tap in the mop sink in the maintenance room) and let the water run for a few minutes.
• Catch some water in a light-coloured cup or container to see if it is clear.
• Restore water to the rest of the building if the water is clear.

What should I do if the water is still discoloured after 2 to 3 hours?
If this happens, contact us.

What if someone accidentally drinks the water when it is discoloured?
Drinking discoloured water should not make you sick, however, it may not smell, taste, or look pleasant.

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

Are you monitoring water quality during the cleaning program?
Yes, our laboratory staff will randomly collect samples and test water quality from hydrants, homes, and businesses during the cleaning program.

Is water main cleaning a waste of water?
No. We are using a unidirectional flushing technique, which uses 40% less water than conventional flushing.

What is unidirectional flushing?
During unidirectional flushing, water system valves are operated to create one-way flow to the 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 towards the outer limits of the city. This ensures that clean water is always used to flush the mains.

What is conventional flushing?
In conventional flushing, the water used to flush the main does not always begin at the clean water source (the water pumping station), and the speed of the water is much lower than during unidirectional flushing. As a result, more water is required to thoroughly clean the water mains.

Are there other benefits to using the unidirectional flushing technique?
In addition to removing more sediment and using less water than conventional flushing, unidirectional flushing tests and exercises the water system valves and hydrants.

Where will you drain the water used in the cleaning program?
In the area we are cleaning this year, we will discharge the water into the street catch basins, which typically flow to the land drainage system, and into the river. We will be using an environmentally friendly product (sodium ascorbate) to remove the chlorine from the water before it is discharged to the catch basins. We will also collect and test samples to determine the quality of the water we discharge to the catch basins.

Do other cities have similar water main cleaning programs?
Many cities have some type of flushing program to clean their water mains (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.

To keep your children safe, keep them away from the work area at all times.