Q2. How much tap water do Torontonians use? 1,498 million litres, is this per day, per month, or per year? (P41)

The City of Toronto produces potable (drinking) water by treating and cleaning raw water taken from Lake Ontario. Clean water is important to our daily lives. We use it for many things such as drinking, cooking and bathing. Hospitals, restaurants and other businesses also rely on fresh, clean water for their operations.

Drinking Water and the R.C. Harris Water Treatment Plant

Whenever you turn on the tap in your Toronto home and fill a glass of water, you take about ¼ of a litre of estimated 514,000 million litres per day treated at one of Toronto's four water treatment plants. Three of the four water treatment plants are spread along the lakeshore and one is located on Centre Island.

• R.C. Harris Water Treatment Plant
• R.L. Clark Water Treatment Plant
• F.J. Horgan Water Treatment Plant
• Island Water Treatment Plant

The oldest and largest of these plants, the R.C. Harris Filtration Plant, is located in the Beaches, at the foot of Victoria Park Avenue. Built in the 1930's, is still fully functional, providing approximately 47% of Toronto and the Region of York's water supply. For over 80 years, it has drawn water from Lake Ontario, then cleaned, disinfected and converted it into safe potable/drinking water for pumping into the City's distribution system.

How does it end up in my glass?

Where do you get that water in your glass? Simply put, water is pumped out of Lake Ontario and pushed back into the City of Toronto once it's clean - into your home. The process sounds simple but in reality involves a complex combination of phases to ensure that the treatment of our drinking water meets or exceeds all standards set for drinking water by the provincial and federal environmental ministries.

Once treated, the plant then pumps water to various reservoirs throughout the City of Toronto and the Region of York. The water isn't just "taken out of the lake", but drawn from under rock deep in the bed of the lake. There is an East and a West Intake; 2,450 millimetre diameter concrete lined steel intake pipes. The intake mouths are located approximately 2,650 meters from shore in 15 meters of water. Prior to entering the plant, the two pipes join into a junction shaft, which is a 3,050 mm diameter tunnel in rock below the bed of the lake about 1,000 meters in length. Once treated, the plant then pumps water to various reservoirs throughout the City of Toronto and the Region of York.

Here's how it works

1. Lake Ontario The water intake pipes extend into Lake Ontario and collect raw water. In some areas of the city, large intake pipes extend as far as 5 kilometres offshore.
2. Screening At the entrance of the plant, we use traveling screens to remove large objects and debris.
3. Chlorine Chlorine is added to the incoming lake water to kill microorganisms. This stage is called prechlorination. Alumisal so added to the water and it causes the small particles such as silt to clump together. T he chemicals are mechanically mixed into the water to form larger groups of particles called "floc".
4. Settling Basin Heavy flocs drop out of the water in a settling tank and collect along the bottom. These are removed from the water. The cleaner water is lef t at the sur face to be drawn off through spillways, which lead to filtering basins.
5. Filtration Filters are made up of layers of graded gravel, fine sand and carbon or anthracite - a coal-like mineral. The layer of sand removes fine bits of floc, algae and silt. Other chemical and physical impurities and most of the biological impurities (bacteria, etc.) are removed. The layer of activated carbon removes taste and odourproducing chemical from the water.
6. Storage The purified water goes into holding basins prior to distribution. Safe levels of chlorine are added to kill any remaining harmful microorganisms and then excess chlorine is removed with sulphur dioxide. The City of Toronto adds fluoride to the water during the treatment process to help prevent cavities.
7. Ammonia The last step in the treatment process is to add ammonia to the water. Ammonia combines with the remaining chlorine to stabilize the chlorine and keep the water safe during its trip from the plant, through distribution pipes to people's homes and businesses.
8. Testing The treated water is tested regularly to ensure quality.
9. Distribution With the help of high lift pumps, reservoirs, and pumping stations, water is distributed to homes, schools and industries.