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Drinking water quality

Ottawa's water quality

Ottawa's water system draws water from the Ottawa River, a plentiful source of clean, very soft water. The river water is treated using the most effective processes and equipment available to remove colour, suspended particles, algae, vegetation, bacteria and viruses. Our water-purification processes are continuously monitored, ensuring that high-quality water is pumped out of the plants and maintained as it travels through the distribution system. The result is water that is sparkling clear, fresh tasting and safe to drink.

Each year, we perform approximately 100,000 water-quality tests in municipal, provincial, federal, private and university laboratories using the most up-to-date technologies and equipment. These tests cover a broad spectrum and provide information on the physical, inorganic, organic, microbiological and radiological characteristics of the water. The results are then analysed to confirm that quality is maintained as the water travels through the distribution system on its way to homes and workplaces in Ottawa.

In addition to these processes and distribution system tests, our water quality specialists are available to respond to customer inquiries and concerns. It's our job to investigate and resolve problems quickly and efficiently. Please feel free to contact us if you have any questions.

Water research

The City of Ottawa is constantly striving to improve the quality of our drinking water, and to optimize the processes we use to treat and distribute water to our customers. We are actively working on a number of process studies and experiments to optimize our existing treatment process.

We are currently evaluating new methods of water purification such as Deferred Chlorination, Ozone, Chlorine Dioxide, Carbon Dioxide, Caustic Soda, Sulphuric Acid, Biofiltration, and Alternative Coagulants, at the City's Pilot Plant Research Facility, located in the Britannia Water Purification Plant. At present, there are 22 projects being carried out in partnership with several Canadian universities and agencies such as Health Canada, and the Research Foundation of the American Water Works Association.

This research allows the City to be proactive in implementing new technologies, providing us with drinking water of the highest quality while at the same time, reducing our operating costs.


Common water quality questions

Answers to the most commonly asked questions about drinking water. If you have a question that is not addressed, please call 3-1-1 (TTY: 613-580-2401).

Taste and odour

  • “Earthy” or “musty” odour: Ottawa's water system draws from the Ottawa River, which has a natural, slightly "earthy” or “musty" odour. This odour is caused by trace levels of natural organic substances produced by plants and algae in the river. The water purification process removes almost all of the odour present in the river water. Some sensitive consumers may still notice an odour, especially when tap water is warmed up (e.g. showering). The odour is not a health concern.
  • “Sulphur” or “septic” odour from your tap: If you notice a "septic” or "sulphur" odour when using the bathroom and kitchen faucets, it is usually caused by decaying hair, dirt and debris that is caught in the drain. It is not coming from your tap water. To check this, fill a glass with cold water and take it immediately to another room in the house. If this water is odourless, the odour is coming from your drain. To correct the problem, the drain must be cleaned physically or with the use of a chemical drain cleaning product. Alternatively, you can pour a small amount of baking soda, followed by vinegar down the drain. Wait a few minutes and then run your cold water tap for one minute.

My water looks cloudy

At times during the year, you may find that your tap water appears cloudy. This is not a health concern. The cloudy water you are experiencing is due to air bubbles that are trapped in the tap water. As the water warms up slightly in your household plumbing and pressure is reduced through your tap fixture, dissolved air will be released resulting in the cloudy white appearance when filling a glass which should disappear within a few minutes. To confirm this, pour some cold water into a glass and observe. You should notice the air bubbles gradually disappear from the bottom of the glass upwards within 1-2 minutes. If the cloudiness persists, call 3-1-1 to arrange for water quality testing.  

Rusty/discoloured water

If the water in your cold water tap or toilet tank is rusty, yellow, or discoloured, this could be a result of sediment coming from the water main. This often occurs when water main construction or fire hydrant maintenance is being conducted in your area. Sudden changes in flow can disturb rusty or iron sediments within older water main pipes. The red/yellow discoloured water is caused by the presence of iron, and while it is not aesthetically pleasing, it does not pose a health concern.

Do I need to filter or boil my water?

You do not need to filter or boil your tap water. Be aware of door-to-door salesmen or imposters making false claims about the City’s tap water being unsafe. Ottawa’s tap water is tested more than 100,000 times a year at 55 different locations. Since 2009, Ottawa-owned water purification facilities have received only perfect scores in annual inspections performed by Ontario’s Ministry of the Environment and Climate Change. If you require additional information or would like to have your tap water tested, please contact 3-1-1 (TTY 613-580-2401). 

Residents serviced by a communal or private well may consider purchasing an in-home treatment system for aesthetic purposes such as taste or odour. For more information, please email or consult the following Health Canada resources before purchasing an in-home water system:

Is there lead in Ottawa's drinking water supply?

Drinking water supplied by the City is lead-free. However, lead can enter drinking water from either lead service pipes or solder containing lead. Both lead and copper piping were used until 1958 when copper water service lines became the standard in the plumbing industry. Lead-based solder was also used for plumbing until the late 1980's when changes to the Plumbing Code prohibited its use. Even with today's standards some bronze fixtures may contain low amounts of lead. 

In homes that have lead service lines, the average lead concentration is 2.3 ppb which is safely below the Health Canada target of 10 ppb for lead. The City of Ottawa adjusts the pH level of treated drinking water in Ottawa’s central system to reduce corrosion of water mains and household plumbing which minimizes the amount of lead that is dissolved in household drinking water. As a result, Ottawa tap water is well within the drinking water standards for lead, even in homes that have lead service pipes supplying the building. 

For information on having your lead service line replaced refer to the Lead Pipe Replacement program.

Particles or sediment in your tap water

Occasionally, particles might be observed in your tap water. There are a few common situations that can lead to particles:

  • White/brown particles: If the particles are white and appear to have a slight brown appearance on one side, it might be a piece of ceramic from the liner of your hot water tank. To check this, the particle should be able to be crushed with a spoon and should fizz when vinegar is added. Contact your hot water tank supplier and have it inspected if you find ceramic particles in your water.
  • Sand or sediment: If the particles appear to be sandy and are observed in the storage tank at the back of your toilet, it is most likely sediment that was disturbed in the water main. Hydrant flushing will generally clear any sediment from the water mains in your area. If the issues persists, contact 3-1-1 to have the hydrant flushed again.
  • Black particles: Black particles can sometimes be small pieces of rubber from a deteriorating gasket or rubber washer in your tap fixture. In some cases, black particles can be caused by the presence of high levels of manganese in a groundwater well. In this case, contact 3-1-1.
  • Reddish/brown: If you observe tiny brown spheres in your tap water, it might be resin beads from a water softener or filtration system. These beads look almost translucent and their presence indicates your water softener needs to be inspected or replaced.

What is the pink stuff in my bathroom?

Many customers report a persistent pink stain in their bathroom, usually on moist surfaces such as tile grout, showerheads, sink drains, or bathtub surfaces. This is usually caused by an airborne bacterium called Serratia marcescens commonly found in air, dust, and soil. These bacteria thrive on moisture, dust, and phosphates and are widely distributed especially in areas under construction or near farms. The bacteria, produces a pinkish or orange film on surfaces that are regularly moist, such as bathroom surfaces. The best solution to keep these surfaces free from the bacterial film is routine cleaning using a disinfectant such as Javex or a bleach-based cleanser. Installing a bathroom fan will also help to minimize the moist environment in bathrooms.

Is there fluoride in Ottawa’s drinking water?

The City of Ottawa adds fluoride to the drinking water. The target level of 0.70 mg/L (ppm) of fluoride in the drinking water is maintained in accordance with a recent study entitled “Findings and Recommendations of the fluoride Expert Panel to Health Canada”. The target level of 0.70 mg/L is within the 0.50 – 0.80 mg/L concentration range for fluoride suggested by the Ontario Ministry of the Environment and Health Canada, where adding fluoride to drinking water is practiced.

Fluoride is not added to the water from the five communal well systems (Carp, Munster, Kings Park, Shadow Ridge and Vars) owned and operated by the City. However, drinking water from these systems may contain naturally occurring fluoride in the range of 0.10 mg/L to 0.70 mg/L.

Water system      

Fluoride concentration

Ottawa central water supply


0.70 mg/L

Carp well system  


0.55 mg/L

Kings Park (Richmond) well system

0.40 mg/L

Munster well system


0.65 mg/L

Shadow Ridge (Greely) well system


0.05 mg/L

Vars well system                                         

0.15 mg/L

Why does the City use chloramine and chlorine?

As part of its ongoing commitment to maintain and improve drinking water quality, the City of Ottawa implemented a new way of disinfecting drinking water in July 1992. Chloramine (a combination of chlorine and ammonia) is now added to the water before it travels through the distribution system. Chloramine is an effective and long-lasting disinfecting agent that is safe for drinking, cooking and bathing.

Chlorine is used in the five communal well systems’ (Carp, Munster, Kings Park, Shadow Ridge, & Vars) water supply. It is added to provide disinfection during treatment and to maintain water quality throughout the distribution system.

Is Ottawa’s drinking water hard or soft?

Water hardness is determined by the amount of calcium and magnesium that is dissolved in water. Ottawa’s water supply is considered very soft, resulting from the natural softness of our source water (Ottawa River). Hard water does not pose any health concerns, however it can lead to scale deposits on hot surfaces such as kettles and hot water tanks.

 Ottawa’s central drinking water supply is about 30 mg/L (ppm) of total hardness which is considered very soft. On the other hand, ground water wells such as the communal well systems often have high levels of hardness due to presence of natural calcium and magnesium minerals. Levels of hardness are shown below for comparison.

Water system      


Ottawa central water supply


30 mg/L  (very soft)

Carp well system  


225 mg/L (moderately hard)

Kings Park (Richmond) well system

270 mg/L (moderately hard)

Munster well system


185 mg/L (moderately hard)

Shadow Ridge (Greely) well system


350 mg/L (quite hard)

Vars well system                                         

100 mg/L (low hardness)