Private wells

How well water gets contaminated

Your well water can be contaminated by:

• openings in the well seal
• improperly installed well casing
• well casing not deep enough
• well casing not sealed
• a source of contamination not related to well construction (e.g. your septic system, pet waste or livestock waste, agricultural or road chemicals)

Preventing contamination

• do not allow liquids or wastes from garbage and manure piles to drain towards the well casing
• do not locate dog runs around the well casing
• do not treat the area around the well with pesticides or fertilizer
• do not flush oils, detergents, paints, solvents or other chemicals down the toilet

Proper installation and maintenance includes ensuring

• sanitary seal or well cap is securely in place and watertight
• cap is at least 40 cm above the ground
• joints, cracks and connections in the well casing are sealed
• surface drainage near the well is directed away from the well casing
• surface water does not pond near the well
• well pump and distribution systems are checked regularly
• changes in the quantity and quality of water are investigated immediately
• well water is tested for bacteria three times a year and after major plumbing work
• wells are chlorinated and tested after any major repairs

Abandoned wells should be carefully sealed to prevent pollution of groundwater and any safety hazards. Hiring a qualified well contractor to seal the well is strongly recommended.

If your well water becomes contaminated,

Other sources of drinking water

Bottled water

While bottled water available in Canada is generally of good quality, it is not necessarily safer or healthier than water from municipal supplies.

The sale of bottled water is not licensed in Canada. However, the federal Health Protection Branch makes spot checks from time to time of both domestic and foreign bottled water. In addition, local health units do regular bacterial testing on all bottled water distribution located in their district.

Municipal water supplies are checked for 350 or more substances. Only three substances must be checked in bottled water. These are bacteria content, fluoride and total dissolved solids (magnesium, iron, sodium).

Bottled water may contain naturally occurring bacteria, which under improper and/or prolonged storage conditions, could increase in numbers to levels that may be harmful to health. Refrigeration is a good way to reduce the growth of these bacteria.

Storage of bottled water may provide an opportunity for bacteria to grow, particularly if the containers were not sterile.

Water from cisterns

The water in cisterns usually comes from rainfall collected off the roof. It is stored in concrete tanks (reservoirs) in the basement or attic.

The water collected can be contaminated from many sources (especially bird droppings) and thus is not safe for drinking.

If a cistern supply exists or is planned, it is recommended that no connections be made between the main water supply and the cistern. Colour coding of the water pipes is also a good idea to ensure that a separation exists.

The use of a cistern supply is not recommended for human bathing or drinking water. Cistern water should only be used for such uses as lawn and garden watering and washing cars.

Wells

There are over 50,000 private wells in the Ottawa area. Well owners are responsible for ensuring that water from their wells is safe to drink, and that their wells are not contaminating the groundwater. Wells must be properly designed and maintained to ensure that drinking water is safe.

Common types of wells: Dug and bored wells (with casings 60 to 120 cm/24 to 48 in.) are less expensive to install than drilled wells. Like sand point wells, dug/bored wells are prone to near-surface contamination and shortages. Drilled wells (casings 10 to 20 cm/4 to 8 in.) cost more but penetrate deeper aquifers.

Cross cut image of a drilled well

Where water comes from

The water we drink generally comes from surface water (above ground) or groundwater (underground). Only about 1% of the Earth's water is surface and groundwater.

The water cycle: Rain or melting snow can take several paths. It can runoff into streams, lakes or rivers. It can seep into the ground to be used directly by plants or to recharge groundwater. It can evaporate and return to the atmosphere. The cycle is complete when water in the atmosphere returns to earth as rain or snow. Groundwater from a deep well may have been in the ground for hundreds or thousands of years. In a shallow aquifer, the water may be a few weeks or years old.

The hydrologic cycle

The Hydrologic Cycle showing how rain or snow runoff pools underground to provide water

How water moves

Groundwater flows from areas of higher elevation and/or pressure to lower elevation and/or pressure. It can flow horizontally or vertically upward or downward but usually in just one direction. This direction of natural flow can be affected or changed by pumping a well. How fast groundwater moves depends on how porous the soil or rock is, and whether the groundwater surface is sloped. The speed of water movement varies greatly.

The water table: The point at which the ground is saturated determines the water table. This level rises and falls depending on rainfall and local water use. Taking water out of the ground faster than it is recharged by the water cycle will lower the local water table.

Contamination

Is it clean? When an aquifer gets contaminated, the water may be unfit and unsafe to use. Groundwater can become contaminated in several ways:

• spills on the ground, e.g., fuel and pesticide spills
• injection into the ground, e.g., septic leaching beds, disposal of waste in wells, contaminated surface water running into poorly constructed or maintained wells
• improper handling of industrial solvents and chemicals
• waste leakage, e.g., manure storage, wastewater, septic tanks and landfills
• leaking underground and above-ground fuel storage tanks
• groundwater travelling from contaminated to clean aquifers
• over-application of manure, commercial fertilizers or pesticides

Whether the groundwater gets contaminated depends on:

• the size or strength of the contamination source
• the ease with which the contaminant can move into or travel through the soil
• out how to protect your well from contamination.

Many residents rely on well systems for their drinking water. The City itself has five well systems and two purification plants to provide drinking water to residents

Find out how to get your well tested, how to prevent contamination and learn about common well problems and solutions. Learn about the City’s well systems and water purification plants and view their annual testing results.

Where water comes from

The water we drink generally comes from surface water (above ground) or groundwater (underground). Only about 1 per cent of the Earth's water is surface and groundwater.

The water cycle: Rain or melting snow can take several paths. It can runoff into streams, lakes or rivers. It can seep into the ground to be used directly by plants or to recharge groundwater. It can evaporate and return to the atmosphere. The cycle is complete when water in the atmosphere returns to earth as rain or snow. Groundwater from a deep well may have been in the ground for hundreds or thousands of years. In a shallow aquifer, the water may be a few weeks or years old.

The Hydrologic Cycle

How water moves

Groundwater flows from areas of higher elevation and/or pressure to lower elevation and/or pressure. It can flow horizontally or vertically upward or downward but usually in just one direction. This direction of natural flow can be affected or changed by pumping a well. How fast groundwater moves depends on how porous the soil or rock is, and whether the groundwater surface is sloped. The speed of water movement varies greatly.

The water table: The point at which the ground is saturated determines the water table. This level rises and falls depending on rainfall and local water use. Taking water out of the ground faster than it is recharged by the water cycle will lower the local water table.

Buying a Home? New Well

New wells must be designed carefully to protect our water resources. Wells must be drilled by a licensed water well contractor, who submits a water well record to the homeowner and the Ministry of the Environment.

Keep well documents safe, as you will need them when you sell your house. Be sure to ask for copies of these records when you are the buyer.

Contacts

Common water quality problems, possible causes and treatments

Project Background

The City of Ottawa has partnered with the Ontario Geological Survey to study groundwater in Western Rural Ottawa. The objective of the study is to develop maps of expected groundwater quality to help support development planning.

Geological Setting

The chemistry of groundwater varies across the study area and depends on several factors that include the local geology, the composition of the rock and soil underground, groundwater flow patterns and nearby land uses. In Eastern Ontario, naturally-occurring groundwater quality with concentrations above Ontario Drinking Water Standards, Objectives or Guidelines can occur due to the marine (salt water) environment that existed in the St. Lawrence lowlands following the most recent glacial period over 10,000 years ago. Parts of Eastern Ontario were covered by the Champlain Sea, which deposited up to 40 metres of marine clay. The thick clays act to trap salt water for a long period of time; some of the groundwater in the study area were assessed to be more than 10,000 years old. In addition, the marine clay covers complex bedrock layers of limestone and shale that may also contribute to poor water quality. Some areas of Eastern Ontario have groundwater with the following chemistry: brackish to saline water; elevated sodium, chloride, iodide and fluoride; elevated pH; and elevated methane.

The West Ottawa study area has large areas of exposed bedrock, where the groundwater aquifers are more vulnerable to contamination. Hydrogeological sensitivity and the protection of groundwater supplies will also be investigated as part of this study.

Study Area

The West Ottawa Groundwater Study boundary is shown in Map 1 (below). Within the City of Ottawa, the Study Area includes Ward 5 (West Carleton-March) and the western portion of Ward 21 (Rideau-Goulbourn).

This study is a continuation of three previous studies within the City of Clarence‑Rockland (pilot study, 2013-2016), the Township of Alfred and Plantagenet (2015-2017) and East Ottawa and Champlain Township (2017-2019). This study will broaden the understanding of groundwater in Eastern Ontario within the former Champlain Sea Basin.

2019 Well Water Sampling Program

A field program to sample raw (untreated) well water from existing private wells was conducted between June and August 2019 as part of the West Ottawa Groundwater Study. Well sampling was conducted on a two kilometre grid creating an even distribution across the study area. The objective was to sample one drilled (deep) well from every two kilometre grid block and one dug (shallow) well from every other two kilometre grid block.

The purpose of the sampling program was to collect high-quality groundwater chemistry information to support aquifer mapping, to determine groundwater age and to understand groundwater flow patterns. The groundwater sampling methods applied in the study follow those developed by the Ontario Geological Survey as part of the Ontario Ambient Groundwater Geochemistry Program.

Well Water Sampling Program at a glance

• 1,050 local residents volunteered to participate
• 307 groundwater wells were sampled in West Ottawa
  • • This included 263 drilled wells and 44 dug wells
• 85 chemical, bacteriological and field parameters were analyzed from each groundwater sample

A summary of the field work completed as part of the West Ottawa Groundwater Study can be found in the following publication:

T. Di Iorio, R.A. Harrison, T. Al, A. Majury and S.M. Hamilton, 2019. West Ottawa Groundwater Study. In Summary of Field Work and Other Activities, 2019, Ontario Geological Survey, Open File Report 6360, p.23-1 to 23-9.

Well Sample Results

Thank you to all residents who volunteered to have their wells sampled as part of the West Ottawa Groundwater Study.

Bacteriological results were provided to all volunteers in 2019.

We had originally planned to have the chemical analysis provided by March 2020. Unfortunately, results of the chemical analyses were delayed due to the COVID-19 pandemic. In May 2022, we were pleased to provide all participating well owners with a copy of the chemistry results of their untreated well water.

Groundwater maps and a final report are expected by late 2022. Please visit this webpage for future updates!

Resources

Information and requirements for groundwater wells in Ontario:

• Ministry of the Environment and Climate Change

Free well water testing offered by your local Health Unit:

• Ottawa Public Health

Geology of Ontario:

• Ontario Geological Survey

Project Background

The City of Ottawa and the United Counties of Prescott and Russell (UCPR) have partnered with the Ontario Geological Survey and South Nation Conservation Authority to study groundwater in East Ottawa and Champlain Township. The objective of the study is to develop maps of expected groundwater quality to help support development planning.

Geological Setting

The chemistry of groundwater varies across the study area and depends on several factors that include the local geology, the composition of the rock and soil underground, groundwater flow patterns and near-by land uses.  In Eastern Ontario, naturally-occurring groundwater quality with concentrations above Ontario Drinking Water Standards, Objectives or Guidelines can occur due to the marine (salt water) environment that existed in the St. Lawrence lowlands following the most recent glacial period over 10,000 years ago. Parts of Eastern Ontario were covered by the Champlain Sea, which deposited up to 40 metres of marine clay. The thick clays act to trap salt water for a long period of time; some of the groundwater in the study area were assessed to be more than 10,000 years old.   In addition, the marine clay covers complex bedrock layers of limestone and shale that may also contribute to poor water quality. Some areas of Eastern Ontario have groundwater with the following chemistry: brackish to saline water; elevated sodium, chloride, iodide and fluoride; elevated pH; and elevated methane. 

Study Area

The East Ottawa – Champlain Groundwater Study boundary is shown in Map 1 (below). Within the City of Ottawa, the Study Area includes Ward 19 (Cumberland) and the eastern portion of Ward 20 (Osgoode).  The western boundary of the study area within Ottawa is the Gloucester Fault; generally groundwater has better drinking water quality on the west side of the Gloucester Fault. 

This study is a continuation of two previous studies within the UCPR in the City of Clarence‑Rockland (pilot study, 2013-2016) and the Township of Alfred and Plantagenet (2015-2017).  Ottawa and Champlain are located directly to the west and east of the previous study areas.  This study will broaden the understanding of groundwater in Eastern Ontario within the former Champlain Sea Basin.

2017 Well Water Sampling Program

A field program to sample raw (untreated) well water from existing private wells was conducted between June 2017 to August 2017 as part of the East Ottawa-Champlain Groundwater Study.   Well sampling was conducted at a two kilometre scale to establish an even distribution across the study area; the objective was to sample one drilled (deep) well from every two-kilometer grid block and one dug (shallow) well from every two two-kilometer grid blocks. The project was advertised (fliers, posters, newspaper ads) prior to the field season and volunteers were selected on a first-come, first-served basis.

The purpose of the sampling program was to collect high-quality groundwater chemistry information to support aquifer mapping, determine groundwater age and interpret groundwater flow patterns.    The groundwater sampling methods applied in the study follow those developed by the Ontario Geological Survey as part of the Ontario Ambient Groundwater Geochemistry Program.

Well Water Sampling Program at a glance

• 775 local residents volunteered to participate
• 239 groundwater wells were sampled
• 165 wells were sampled in East Ottawa (121 drilled wells, 44 dug wells)
• 74 wells were sampling in Champlain Township (54 drilled wells, 20 dug wells)
• 82 chemical, bacteriological and field parameters were analysed from each groundwater sample

A summary of the field work completed as part of the East Ottawa–Champlain Groundwater Study can be found in the following publication:

T. Di Iorio, M. Melaney, S. Foubister and S.M. Hamilton, 2017.  East Ottawa–Champlain Groundwater Study.  In Summary of Field Work and Other Activities, 2017, Ontario Geological Survey, Open File Report 6333, p.27-1 to 27-8. 

Next steps

Well water sampling results will be available to well volunteers in spring 2018; all volunteers will receive a copy of the chemical results from their untreated well water and a summary report.  

Groundwater maps and a final report are anticipated by late 2018.  Please visit this webpage for future updates!

Resources

• Information and requirements for groundwater wells in Ontario
  Ministry of the Environment and Climate Change
• Free well water testing offered by your local Health Unit:
  Ottawa Public Health
• Eastern Ontario Health Unit (United Counties of Prescott and Russell)
• Geology of Ontario:
  Ontario Geological Survey

Project Background

The City of Ottawa has partnered with the Ontario Geological Survey to study groundwater in Southern Rural Ottawa. The objective of the study is to develop maps of expected groundwater quality to help support development planning.

Geological Setting

The chemistry of groundwater varies across the study area and depends on several factors that include the local geology, the composition of the rock and soil underground, groundwater flow patterns and near-by land uses. In Eastern Ontario, naturally-occurring groundwater quality with concentrations above Ontario Drinking Water Standards, Objectives or Guidelines can occur due to the marine (salt water) environment that existed in the St. Lawrence lowlands following the most recent glacial period over 10,000 years ago. Parts of Eastern Ontario were covered by the Champlain Sea, which deposited up to 40 metres of marine clay. The thick clays act to trap salt water for a long period of time; some of the groundwater in the study area were assessed to be more than 10,000 years old. In addition, the marine clay covers complex bedrock layers of limestone and shale that may also contribute to poor water quality. Some areas of Eastern Ontario have groundwater with the following chemistry: brackish to saline water; elevated sodium, chloride, iodide and fluoride; elevated pH; and elevated methane.

Study Area

The South Ottawa Groundwater Study boundary is shown in Map 1 (below). Within the City of Ottawa, the Study Area includes parts of Ward 20 (Osgoode) and Ward 21 (Rideau-Goulbourn).

This study is a continuation of three previous studies within the City of Clarence Rockland (pilot study, 2013-2016), the Township of Alfred and Plantagenet (2015-2017), East Ottawa and Champlain Township (2017-2019) and West Ottawa (2019 – 2022). This study will broaden the understanding of groundwater in Eastern Ontario within the former Champlain Sea Basin.

2022 Well Water Sampling Program

A field program to sample raw (untreated) well water from existing private wells was conducted between June through October 2022 as part of the South Ottawa Groundwater Study.  Well sampling was conducted using a two-kilometre grid to establish an even distribution across the study area; the objective was to sample one drilled (deep) well from every two-kilometer grid block and one dug (shallow) well from every other two-kilometer grid blocks. The project was advertised (fliers, posters, newspaper ads) prior to the field season and volunteers were selected on a first-come, first-served basis.

The purpose of the sampling program was to collect high-quality groundwater chemistry information to support aquifer mapping, determine groundwater age and interpret groundwater flow patterns. The groundwater sampling methods applied in the study follow those developed by the Ontario Geological Survey as part of the Ontario Ambient Groundwater Geochemistry Program.

Well Water Sampling Program at a glance

• 1,400 local residents volunteered to participate
• 327 groundwater wells were sampled in West Ottawa
  • This included 317 drilled wells and 10 shallow dug wells
• 87 chemical, bacteriological and field parameters were analyzed from each groundwater sample

A summary of the field work completed as part of the South Ottawa Groundwater Study can be found in the following publication:

T. Di Iorio, S. Foubister and C.S. Bocking, 2022. South Ottawa Groundwater Study . In Summary of Field Work and Other Activities, 2022, Ontario Geological Survey, Open File Report 6390, p.25-1 to 25-9.

Next steps

Thank you to all the residents who volunteered to have their wells sampled as part of the South Ottawa Groundwater Study.  Bacteriological results were provided to all participants in 2022 and we had originally planned to have the chemical analysis provided by March 2023.  Unfortunately, there has been significant unforeseen setbacks and complications at the Ontario Geological Survey laboratory that analyses about 75% of the 87 groundwater parameters for this project. The program is prioritizing maintaining a high level of data quality and therefore we will wait for the laboratory issues to be fully resolved.  We sincerely apologize for the long delay.

Water quality results were received from the Ontario Geological Survey to City staff in late August 2024.  Results underwent thorough quality control verification. City staff are preparing letters with individual results for well owners, which will be provided by mail before the end of September 2024.  Many thanks to all the resident volunteers for your patience.

In 2025, the City will be interpreting the groundwater chemistry data obtained from this study to create regional maps of expected aquifer quality to help support future development planning and aquifer protection.

Please visit this webpage for future updates!

Resources

Information and requirements for groundwater wells in Ontario:

• Ministry of the Environment and Climate Change

Free well water testing offered by your local Health Unit:

• Ottawa Public Health

Geology of Ontario:

• Ontario Geological Survey