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What's in your water?


What is fluoride?

Fluoride is a mineral that occurs naturally in soil, air and water. Fluoride helps to prevent tooth decay by re-mineralizing cavities when they first begin to form and increasing the resistance of tooth enamel to acids that cause tooth decay. Research has shown that people of all ages who regularly consume drinking water that has been fluoridated within recommended ranges, have between 15 - 40% fewer cavities.

Does Ottawa’s drinking water contain fluoride?

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, where fluoridation of drinking water is practiced.

Fluoride is not added to the water from the five communal well systems (Carp, Munster, Richmond, 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.

Why does Ottawa add fluoride to drinking water?

Under the direction of the Medical Officer of Health, Ottawa adds fluoride to adjust the natural concentration of the water supply to the level recommended for optimal dental care. This is a public health measure in accordance with provincial guidelines for drinking water and recommendations supported by the Ontario's Ministry of Health, Health Canada, the World Health Organization and American and Canadian Dental Associations.

Who monitors the level of fluoride in drinking water?

The fluoride level is continuously monitored at both City water treatment plants and by certified operators throughout the water disitrubiton system. The results of the monitoring program are reviewed by Ottawa Public Health.

How is fluoride added to the drinking water?

The City of Ottawa uses Hydrofluorosilicic acid ( HFS ) to fluoridate drinking water. It comes in the form of a liquid solution that is delivered to the treatment plant in tanker trucks. Liquid HFS is added to drinking water during the final stage of the water treatment process. All chemicals used in water purification must be approved for application in potable water and must meet a number of product quality standards.

What about health concerns of adding fluoride to drinking water?

The possible effects of fluoride in drinking water is one of the most intensely researched areas of public health with several hundred recent publications. A number of recent, major reviews have been commissioned by governments around the world to examine the potential for adverse health effects related to fluoride (Australia, United Kingdom, United States, and Canada). As part of our ongoing review, the Ottawa Public Health Department has reviewed these major studies. All concluded that water fluoridation is a safe and effective method of reducing tooth decay at all stages of life.

To find out more about the benefits of fluoride, please visit Ottawa Public Health’s dental health web page.

What happens when the supply is interrupted?

Occasionally we stop adding fluoride for short periods during equipment maintenance and inform the Medical Officer of Health and the Ontario Ministry of the Environment of the interruption. When the interruption is finished we resume adding fluoride at the same level. We do not lower or raise the concentration to make up for interruptions in supply.

In-home water treatment systems

How safe is my drinking water?

If you are part of the municipal water distribution system, your drinking water meets or is better than all provincial and federal drinking water standards. The City constantly monitors and tests its drinking water in accredited laboratories to ensure compliance with the Guidelines for Canadian Drinking Water Quality (Health Canada) and the Ontario Drinking Water Standards (Ministry of Environment) which provide the standard for safe drinking water. Municipal water does not require further treatment in the home.

Is the manufacture and sale of water treatment devices currently regulated in Canada?

The manufacture and sale of water treatment devices for home use is not regulated in Canada. The National Sanitation Foundation (NSF) in consultation with Health Canada has developed voluntary performance standards for water treatment devices and certification by the NSF is the only guarantee that a device can meet specified performance standards for removal of specific contaminants. For more information visit:

What types of in-home water treatment devices are available?

There are four major types of in-home water treatment devices:

  1. Granular activated carbon filters: Filters that can remove colour, taste, odours and some chemicals (certain types of organic chemicals, pesticides and chlorines) from water. Granular activated carbon filters by themselves will not remove lead and other heavy metals.
  2. Reverse osmosis units:  A reverse osmosis unit primarily removes dissolved salts, minerals and metals from the water.
  3. Distillation systems: Water distillation systems remove salt, minerals and heavy metals. They are typically not effective at removing organic compounds such as pesticides and trihalomethanes (THMs). Some distillation units also include a carbon filter that may remove organic compounds
  4. Water softeners: Dissolved calcium and magnesium make water “hard” when present in high concentrations. Water softening units (also called ion exchangers) remove calcium and magnesium ions from water and replace them with sodium ions. A water softener requires the regular addition of salt to regenerate itself and work properly.

Note: There are other devices on the market designed for disinfection of water from private wells, lakes, rivers or ponds. For more information on disinfection devices visit Health Canada’s website.

Should I buy an in-home water treatment device?

This is a personal decision. Water supplied by the City is well within federal and provincial guidelines and standards, is safe to drink and does not require further treatment in the home.

What if my water supply comes from a private well?

If you are not serviced by the City water distribution system and you rely on a private well, you should test your water supply on a regular basis. Groundwater quality varies across the City and your supply may benefit from a water treatment device to make it either safe to drink or to solve taste or odour problems. For further information on water treatment devices for well systems, contact the City of Ottawa Health Services or the Ministry of Environment (MOE) or contact our Water Information Line at 560-6089 and request the How Well is Your Well booklet in the publications section.

Common questions about chloramine

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.

Why does the City use chloramine?

Here's why the City switched from using chlorine to chloramine:

  • Chloramine is a more stable and persistent disinfectant. It preserves the quality of the purified water as it travels through Ottawa's large and expanding water distribution system;
  • Chloramine helps to reduce disinfection by-products such as trihalomethanes (THMs) in the water;
  • Chloramine reduces the taste and odour of chlorine in tap water.

Is chloramine safe?

Yes. Chloramine has been used safely in Canada and the United States for years. Many water utilities are in the process of switching to chloramine because of its benefits.

The Ontario Ministry of Environment (MOE) and Health Canada recognize chloramine as a safe disinfectant that reduces the formation of disinfection by-products and disease-causing organisms. Chloraminated water is safe for drinking and all water uses.

Note: Kidney dialysis patients must take special care with chloraminated water. 

What are trihalomethanes (THMs)?

THMs are chemical compounds that form when chlorine mixes with naturally occurring organic material in water. These compounds are suspected carcinogens. The MOE and Health Canada have set a standard of 100 parts per billion (ppb)* as the safe maximum level of THMs in drinking water, based on a lifetime of consumption.

*Note: one ppb is comparable to one second in 32 years, or 1¢ in $10,000,000.

Does the City’s water meet the standard for THMs in drinking water?

Yes. The use of chloramine instead of chlorine as a purification agent has reduced the average yearly concentration of THMs to 40 ppb, well below the 100 ppb limit.

Does using chloramine increase the cost of water?

No. The cost of using chloramine is about the same as using chlorine.

Do home water softeners remove chloramine?

Most water softeners are not designed to remove chloramine.

Does bottled water have chloramine?

Normally it does not. Bottled water could contain chloramine if the company uses water supplied by the City as its water source.

Does the pH of water remain the same with chloramine?

Yes, the pH remains the same. The normal pH range for the City's water is 8.4 to 8.8.

What does chloraminated water taste like?

Chloramine itself is colourless, tasteless and odourless. In comparison to chlorinated water, chloraminated water does not have a strong chlorine taste.

If chloramine is such an effective disinfectant, why is it not used in every community?

While the public often considers all drinking water to be the same, the local raw water and water distribution conditions determine the best option for each particular community. Both chlorine and chloramine have their own advantages and disadvantages. Given sufficient contact time, chloramine is as effective as chlorine in destroying bacteria. While chlorine works more quickly, it does not last as long in the water as chloramine.

Is chloramine safe for swimming pools?

Yes. Your pool still requires a free-chlorine residual to delay algae and bacterial growth. Test kits measure free-chlorine residuals and can be used with confidence. Contact your local pool supply store for details.

Is it okay to use chloraminated water on plants, vegetables and fruit trees?

Yes. The small amount of chloramine present in the water should not affect plants of any type. Beneficial bacteria are generally protected by the soil in which they live.

What is Ottawa doing to further improve the quality of drinking water?

The City is carrying out a number of process studies and experiments to optimize our existing treatment process. New methods of water purification such as ozone and bio-filtration are being tested at the City's Pilot Plant Research Facility, in partnership with several universities. These initiatives are underway to continually improve water quality and to better serve the needs of our expanding community.

Common questions about chlorine

Why is chlorine used to disinfect drinking water?

Chlorine has been used since 1911 to disinfect drinking water supplies around the world. It is a strong oxidant that kills bacteria and viruses that are harmful to human health.

What are trihalomethanes (THMs) and where do they come from?

THMs are formed when chlorine reacts with naturally occurring organic material in water. The organic material comes from decaying vegetation. When chlorine is used in the purification of drinking water, THMs are an inevitable by-product. THMs are suspected carcinogens.

What are the major factors that influence THM formation?

There are three major factors which contribute to the formation of THMs:

Chlorine Dose:

Chlorine is used in the water purification process to kill bacteria. Bacterial growth is at its highest in the summer. Therefore, more chlorine is used in the summer to keep bacteria levels in check. As the chlorine level increases, the formation of THMs also increase.

Water Temperature:

Because the source water is warmer in summer than at other times of the year, THMs form more quickly and in larger amounts during the summer months.

Organic Content:

Both the type and amount of organic matter in the source water can increase THM levels.

What is the allowable limit for THMs in our drinking water?

The current provincial standard and federal guideline is 100 ppb*. This guideline is outlined in Ontario Drinking Water Standards produced by Ontario.

*Note: One ppb is comparable to one second in 32 years, or 1¢ in $10,000,000.

What are the current levels of THMs in our central supply of drinking water?

The current yearly average of THMs is 40 ppb well below the federal/provincial drinking water limit. Ongoing monitoring of THMs occurs at both purification plants and throughout the distribution system.

How are guidelines determined?

A federal/provincial committee establishes national guidelines for certain substances that are known or suspected to have adverse effects on health. The THM guideline is designed to safeguard health, assuming lifelong consumption of drinking water.

How do we purify water at the purification plants?

Ottawa's drinking water is drawn from the Ottawa River and is treated at purification plants located at Lemieux Island and Britannia. Chlorine is used twice in the water purification process to kill bacteria.

  1. Disinfection at the Purification Plants
    As the river water enters the purification plants, enough free chlorine is added to kill bacteria, viruses, algae, etc.
  2. Disinfection in the Distribution System
    As the treated water leaves the purification plant, chloramine (chlorine mixed with ammonia) is added to preserve water quality as it travels through the distribution system. Chloramine is a very stable and long-lasting disinfectant. These are important characteristics considering the size of Ottawa's distribution system.

What are the benefits of using chloramine?

There are three primary reasons:

  • to provide a more stable and persistent disinfectant throughout the water distribution system;
  • to help reduce the levels of disinfection by-products such as THMs in the water;
  • to reduce the taste and odour of chlorine in tap water.

What is the City doing to reduce THM levels and to further improve the quality of drinking water?

The City is carrying out a number of process studies and experiments to optimize our existing treatment process. New methods of water purification and new disinfection strategies are tested at the City's Pilot Plant Research Facility, in partnership with several universities. These initiatives are underway to continually improve water quality and to better serve the needs of our expanding community.

Do I have to worry about THMs in my drinking water if I have a private well?

No, you should not be concerned as THMs are formed when chlorine reacts with organic material. Groundwater does not normally contain organic material, as it does not come into contact with vegetation. If you do use chlorine to disinfect your well water, the THM level will be very low.

Is the City's Medical Officer of Health satisfied with the quality of Ottawa's drinking water?

Yes. The Medical Officer is satisfied with the overall quality of drinking water in Ottawa and the efforts of the City to reduce levels of THMs. The City of Ottawa Health Services routinely review the results of the City’s ongoing water quality monitoring program.

Lead in drinking water

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

Lead and drinking water

Q: Is there lead in Ottawa's drinking water supply?

A: Drinking water supplied by the City is lead-free. However small amounts of lead can dissolve into drinking water during contact with plumbing materials such as lead pipes, brass fixtures, and lead solder in the homes of residents. Average lead concentrations in Ottawa’s tap water are well below the Health Canada target of 10 ppb (parts per billion) and are as follows:

  • 0 ppb leaving water treatment plants
  • 0 ppb for tap water in the majority of Ottawa homes (85%)
  • 1.5 - 3.5 ppb in homes with lead service pipes

In order to monitor lead levels in Ottawa, City staff test water samples from 100 homes supplied by lead service pipes.  On very rare occasions, some homes experience lead levels higher than 10 ppb. For example, during 2015 testing, only 4 out of 222 samples had lead levels higher than 10 ppb. Typically these levels are found in properties with service lines supplying their home. These homeowners are notified immediately and provided with practical advice for reducing lead in their tap water in addition to further water quality testing.  

Q: What is the current limit for lead in drinking water?

A: Health Canada and the province of Ontario have established a maximum concentration for lead in drinking water of 10 parts per billion (ppb). This concentration aims to protect infants, young children and children in-utero who are most at risk of exposure to lead. Due to increasing concerns about negative health effects in children, the proposed maximum concentration has been lowered to 5 ppb for drinking water.

Q: Should I be concerned about exposure to lead in drinking water?

A: Exposure to small amounts of lead can be harmful to human health, especially for infants, young children and children in-utero. Lead is present in several environmental sources including soil, dust, food, air, and drinking water. Generally, household dust and food represent the highest lead exposure for young children. Although the lead contribution from tap water is generally low, it can be significant in some homes with lead service pipes.

Q:  Is lead a concern in my children’s school or day nursery?

A:  All schools and day nurseries in Ontario are required to flush plumbing and test water for lead on an annual basis.  Ottawa Public Health works with these operators to ensure any problems detected are resolved and they comply with the Ontario Drinking Water Standards for lead in drinking water. More information is available on the Ontario MOECC (Ministry of Environment and Climate Change) website.  

Q: If the tap water lead concentration is below the maximum allowed concentration, why is the City of Ottawa evaluating different treatment options?

A: To meet possible changes in future lead regulations, the City is evaluating different treatment processes, including the optimization of its current pH control process. Different treatment options are explored on an ongoing basis to ensure the most current and effective processes are in place to protect public health.

Q: Is bottled water lead free?

A: Bottled water comes from various sources and is subject to inspection by the Canadian Food Inspection Agency under the Food and Drugs Act. Most brands of bottled water have low or non-detectable concentrations of lead and the lead concentration is normally displayed on the bottle.Specific questions and concerns should be addressed to the company directly.

Q: How does lead enter drinking water?

A: There are no lead water mains in the City’s water distribution system, however lead service pipes connecting water mains to properties still exist in many homes built before 1960. Trace amounts of lead can dissolve into drinking water as it travels through lead pipes and through contact with household plumbing that contains brass or lead solder. Lead can also dissolve when water sits for lengthy periods (a few hours or more) in the lead service pipe or household plumbing.

Who is impacted?

Q: Who is impacted by lead in drinking water?

A: Approximately 30,000 homes in Ottawa constructed before 1960 and originally built with lead water service pipes. Residents may be impacted if lead service pipes have not been replaced.

Q: How do I know if I have a lead service pipe?

A: If your home was built after 1960, you do not have a lead service pipe. The best way to determine if a service pipe is lead or copper is to scratch the pipe with sandpaper to expose the bare metal. Lead pipes are dull grey in colour and are easily scratched by a hard object. Copper pipes are red-brown and corroded portions may show a green deposit. The water pipe servicing your home should be located in the basement.  A water quality test can also indicate if lead service pipes are present in your home.

Q: What is a water service pipe?

A: A water service pipe connects a building to a municipal water main. Property owners are responsible for the pipe up to their property line and the City owns and maintains the pipe from the property line to the water main.

Q: Are commercial and multi-residential properties impacted?

A: No. Lead is not a suitable material for larger diameter pipes used in large buildings and has therefore not been used. Stronger materials such as copper, iron, or plastic are typically used to supply water to these buildings.

Q: Who is responsible for replacing water service pipes?

A: Property owners are responsible for maintaining the pipe up to their property line and the City maintains from the property line to the water main. Whenever a water main is replaced or upgraded, the City replaces the public portion of lead service line with copper.

Property owners are encouraged to take advantage of the Lead Pipe Replacement program if their home was constructed prior to 1960. If the water service on private property is made from lead, residents can choose to replace it at their cost, and the City in turn will replace the public portion of the service pipe at the City’s cost. The cost to the property owner is generally between $2,000 to $4,000. These estimates do not include the removal and salvage of items such as furniture and fixtures, gardens, landscaping, decks, porches and interior work or finishes and the repair or replacement of these items upon the completion of the water service replacement.

Q: What is the City doing to reduce the risk of exposure to lead?

A: Before treated water enters the distribution system, the City adjusts the pH to minimize the amount of lead and other metals that can dissolve into tap water. To meet future regulations, the City is evaluating alternative treatment options that will further reduce lead concentrations and protect water mains. The City also monitors tap water lead concentrations in older homes through an extensive water quality testing program.

Q: Why do I have lead in my drinking water if I have copper pipes and no lead water service?

A: Lead may be present in solder used to join copper pipes and may also be present in brass fittings and plumbing fixtures. However, lead contributions from brass and lead solder are typically quite low in the range of 1 ppb or less.

What can impacted residents do?

Q: I live in a home with lead plumbing, what should I do?

A: Concerned residents in homes with lead plumbing can:

  • Run their tap for approximately 2 minutes to flush stagnant water sitting in their service pipe prior to cooking or drinking (cost of water would be approximately 2 cents for 2-min tap flushing).
  • Contact the City at 3-1-1 to have their tap water tested for lead (no charge for this).
  • Use an in-home filter designed to remove lead from tap water that is used for drinking and cooking.
  • Take advantage of the Lead Pipe Replacement program – a cost sharing program whereby the City covers the cost of replacing the public portion of the lead service pipe and the resident pays for the private portion with the ability to repay over time.

Q: Who can I call to test my water?

A: Contact the City of Ottawa at 3-1-1 (TTY: 613-580-2401) to have your tap water tested – there is no cost for this service.

Q: Will my home water filter remove lead from drinking water?

A: A pitcher-style filter will reduce lead levels in your drinking water by about 90%. It is recommended that any point-of-use filter unit be certified to meet the appropriate NSF/ANSI Standard 53 for the removal of lead. This information can be found on the label. To completely remove lead, the use of a reverse osmosis or distillation treatment system may be required.

Q: Will boiling water remove the lead?

A: No, boiling your water does not remove lead. If boiled, the lead concentration of the water can actually increase slightly as the water evaporates.

Q: If I have lead service pipes, is it safe to wash dishes, clothing and shower?

A: Yes. Residue on clothing and dishes will not impact your health. Your skin will not absorb lead during bathing or showering.

Q: Who do I call if I have questions or concerns about water quality?

A: Contact the City of Ottawa at 3-1-1 (TTY: 613-580-2401) if you require additional information or have questions about lead in Ottawa’s drinking water. You can also visit Health Canada's website for more information on lead and human health.