Systems Overview: Water, Sewer, Stormwater
The City of Markham is proud of its water distribution, wastewater collection, and stormwater management systems provided and maintained for our residents, businesses, and industries.
Learn more about where our water comes from, what wastewater is and how stormwater is managed.
The City of Markham delivers safe and reliable drinking water.
Through a system of pipes, valves, hydrants, pumping stations, and reservoirs, we deliver high quality, reliable drinking water to our residents and businesses. Learn about where Markham’s water comes from and how it gets treated, tested and delivered to your home.
- Drinking Water Treatment
Markham's water comes from Lake Ontario. It is treated in the City of Toronto and sometimes Peel Region. Water from Lake Ontario has has contaminants that can be harmful to us if we don’t clean the water. These include:
- Physical: materials that don't dissolve in water and make the water appear "dirty"
- Chemical: substances dissolved in the water from natural and manmade processes
- Biological: viruses, bacteria, algae, and other small living organisms (City of Toronto).
We treat water to meet the standards of the Ontario Safe Drinking Water Act, 2002. Markham’s water is monitored at all times for quality.
For a closer look at the treatment process, visit the City of Toronto website for more information.
Disinfection with Chloramine
The City of Toronto's water treatment facilities disinfect water using chloramine. It's a chemical compound that contains chlorine and ammonia.
Chloramination is the process of adding chloramine during the treatment process. This disinfects and kills microorganisms such as viruses, bacteria, and algae. Chloramine is used instead of chlorine because it lasts longer in the distribution system. It makes the water more resistant to contamination as it travels from Toronto to Markham.
Chlorine has been a safe and reliable tool for over a century. It's stopped the spread of waterborne disease. If you don't like the smell a chlorine in your drinking water, fill a pitcher and let it stand overnight in the refrigerator.
Fluoridation
Fluoride is a mineral that occurs naturally in the environment. It's found in soil, air, and water. Fluoride is added at the end of the water treatment process to help prevent tooth decay. Many dentists and health experts want cities to add Fluoride to water. Long-term scientific studies also show that it is helpful and safe.
- Water Distribution System
After treatment, clean water is pumped to York Region. York Region does more testing, storage, and provides additional pressure for Markham's system. Markham then distributes the water to residents and businesses.
Markham's distribution system provides high quality treated water to about 350,000 customers daily. It has:
- Over 1,000 kilometres of watermains
- 11,000 watermain valves
- 8,500 municipal fire hydrants
Markham is a distribution-only system. We don’t own treatment, pumping, or storage facilities. Markham's water is tested to meet Ontario Regulation 170/03 standards. Licensed Waterworks staff collect water samples. These samples are analyzed at Caduceon Environmental Laboratories.
Watch this "Markham's Water Distribution System" video to learn more!
- Property Owner VS City Responsibility
How it's all connected
The City is responsible for the public portion of the water distribution system – spanning from the water main to the municipal property line. Beyond the property line is the private portion of the system and is the responsibility of the property owner. If you suspect there is an issue with any component that the City is responsible for, please contact the Customer Contact Centre at customerservice@markham.ca or 905.477.5530.
Markham's Responsibility
- Service (Curb) Box: Protects the curb stop valve and should be secured and flush with the ground. Never touch or cover it.
- Curb Stop Valve: Located underground, this valve controls the flow of water from the water main to your property.
- Remote Meter Reading Device: A small box mounted on the exterior of your property that allows the City to obtain meter readings without entering the premise.
- Water Mains: More than 1,000 kilometres of underground pipes throughout the City that carry water to water service lines.
- Service Connection: The part of the pipe that runs from the water main to the curb stop valve in front of your property.
- Water Meter: Records the volume of water used by your property.
Property Owner's Responsibility
- Water Service Line: Pipe that runs between the curb stop valve and your property.
- Indoor Water Shut-off Valve: Shuts off the water supply to your property.
- Indoor Plumbing: The system of water pipes, drains, fittings, valves and fixtures in your building that distribute water.
Property owners shall provide free, clear and unobstructed access to the water meter at all times. Tampering or any alteration to the water meter is prohibited under the City’s Water Use By-law 2019-53.
- Markham's Tap Water
It's safe to drink Markham's Tap Water because it's…
- Healthy — a great calorie-free alternative to sugary drinks or caffeine
- Convenient — delivered right to your home or workplace
- Inexpensive — 1000 times less expensive than bottled water
- Well-Tested — Waterworks staff test Markham water several times a day
- Green — bottled water creates unnecessary waste and litter. It also takes energy to bottle, package, cool, and move.
Markham does not have a lead issue as the City does not have any lead pipes in our water distribution system on the public side.
Get a reusable water bottle and bring it with you! Reduce the amount of waste created by single-use plastic bottles.
"Our top priority is providing high quality drinking water to all our customers. We are constantly testing to ensure all standards and regulations are met for a safe, clean and healthy drinking water supply". — Eddy Wu, Director of Environmental Services
What is Wastewater?
Wastewater is any and all water that is used in industrial, commercial or residential buildings that goes down a drain. Wastewater is produced through actions such as doing the laundry, taking a shower or even flushing a toilet. This water then flows into pipes specifically made for wastewater and enters Markham’s sanitary sewer system.
- Wastewater Collection
The City of Markham's sanitary sewer system collects and moves domestic/industrial wastewater to the Duffin Creek Wastewater Pollution Control Plant located in Pickering, Ontario.
There are pipes throughout your home that only collect wastewater. These pipes are a homeowner's responsibility. They include the drains leading from kitchen sinks, toilets, and showers. Keep these pipes free of debris - like hair or grease - to keep them functioning properly.
The section of sewer pipe that runs beneath your home to the property line is also a homeowner's responsibility. If that section of pipe gets clogged with large objects being flushed down a toilet, baby-wipes, grease buildup, or by tree roots on your front lawn, it is the homeowners' responsibility to have it cleared out.
Baby-wipes go into the garbage and should not be flushed, even if they say "flushable" on the package. Hair and grease into the green bin and not into the wastewater system. Sewer backups are commonly caused by items that should never be flushed down the toilet or poured down the drain.
- CLI ECA and Annual Wastewater Collection System Performance Report
The Ministry of Environment, Conservation and Parks (MECP) has introduced a new approach to the Consolidated Linear Infrastructure Environmental Compliance Approval (CLI ECA) program as a modernized approach for streamlining approvals to low-risk routine alterations for the wastewater collection system. The CLI ECA replaces the need to apply for multiple ECAs for every change or alteration (previous pipe to pipe/transfer of review program) into one permission for each system.
City of Markham’s Wastewater Collection System CLI ECA (Approval 021-W601) - Issue 2 [PDF]
The Wastewater Collection System consists of infrastructure designed for the collection and transmission of sewage, including a separate sewage system and pumping stations. The Annual Wastewater Collection System Performance Report includes key topics such as operation, monitoring, inspections, maintenance, repairs, support programs, improvements, and alterations/approvals issued under CLI ECA. The report was completed to meet the requirements as set in the City’s Wastewater Collection System CLI ECA (Approval 021-W601). For more information, please see the 2025 Annual Wastewater Collection Performance Report.
- Wastewater Treatment
The City of Markham's sanitary sewer system collects and moves domestic/industrial wastewater to the Duffin Creek Wastewater Pollution Control Plant located in Pickering, Ontario. The Region treats wastewater and releases the cleaned water into Lake Ontario. The quality of the water being released after treatment must meet high standards as set by the Ministry of the Environment, Conservation and Parks.
Once Markham's wastewater reaches the Duffin Creek Wastewater Pollution Control Plant, it goes through an extensive cleaning process. This process includes four general steps.
Step 1: Screening
As wastewater (sewage) enters the Plant, screening removes large, inorganic objects. These objects could include things such as rags, diapers, personal hygiene products, and any other inorganic objects which are removed and sent to landfill.
Step 2: Primary Treatment (Physical)
Organic materials (ie. human waste and food) in the wastewater are removed using settling tanks. These settlement tanks work by using gravity and time to allow the solids to settle to the bottom of the tank where it is collected. A skimmer is then used to remove fats, oils, and grease that float to the top and a chemical is added to remove phosphourous. The remaining liquid portion of the wastewater moves on to secondary treatment.
Step 3: Secondary Treatment (Biological)
Secondary treatment removes small pieces of organic materials from the wastewater using aeration lanes which pump air into the tanks giving helpful bacteria the oxygen they need to break down the organic material and absorb nutrients. Settling tanks are used again to allow the material and bacteria to settle to the bottom where they are collected and removed. The clean water (effluent) from this stage then flows into its final stage, disinfection.
Step 4: Disinfection
Chlorine (sodium hypochlorite) is added to kill and deactivate any remaining harmful bacteria (i.e.. E.coli.). Afterwards, another chemical, sodium bisulphite, is used to remove the chlorine before the clear treated water is released into Lake Ontario.
- Sewer Backups
Flooding of the sanity sewer system can occur on residential/industrial property, or on public and city regulated property. Sanitary sewer backups can be a result of blockages or pipe breaks.
Blockages occur because of excess grease, food or any other materials such as wet wipes, flushed or poured down the drain. This material accumulates in pipes and restricts the flow, causing a backup. Breaks in underground pipes may happen due to faulty installation, pipe age, digging, or invading tree roots.
The City of Markham will repair any blockages or breaks on the Markham-owned portion of the pipes as quickly as possible. However, pipes in a residential/industrial building, as well as the underground pipes from the building to the property line, are the responsibility of the property owner.
What is Stormwater?
Stormwater is water that originates from precipitation, such as rain or melting snow, that flows over land or infiltrates the ground before entering storm sewers and natural water bodies. At the City of Markham, stormwater that runs off our communities is managed through system infrastructure that is transported and treated to control flow, prevent flooding, reduce erosion, protect infrastructure, and maintain the health of waterways.
- Stormwater Management
The City of Markham, its residents and businesses value our environment and its natural resources. Our stormwater management activities help protect and enhance our water resources, and maintain the continued health of our streams, rivers, lakes, fisheries and natural heritage systems. Stormwater management policies and practices also help manage the risk of flood damages in natural and urban drainage systems.
- CLI ECA and Annual Stormwater Management System Performance Report
The Ministry of Environment, Conservation and Parks (MECP) has introduced a new approach to the Consolidated Linear Infrastructure Environmental Compliance Approval (CLI ECA) program as a modernized approach for streamlining approvals to low-risk routine alterations for the stormwater management system. The CLI ECA replaces the need to apply for multiple ECAs for every change or alteration (previous pipe to pipe/transfer of review program) into one permission for each system.
City of Markham’s Stormwater Management System CLI ECA (Approval 021-S701) [PDF]
The Stormwater Management System consists of infrastructure designed for the collection and treatment of stormwater, including a separate stormwater system, management facilities, and pumping station. The Annual Stormwater Management System Performance Report includes key topics such as system operation, monitoring, inspections, maintenance, repairs, support programs, improvements, and alterations/approvals issued under the CLI ECA. The report was completed to meet the requirements as set in the City’s Stormwater Management System CLI ECA (Approval 021-S701). For more information, please see the 2025 Annual Stormwater Management System Performance Report.