Possible Health Effects of Drinking Contaminated Well Water

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Many Halton Region residents, living primarily in rural areas, rely on private wells, cisterns or other privately-owned water sources for their drinking water.

Municipal water supplies in cities and towns are maintained and tested by Halton Region. However, privately-owned wells are the responsibility of the homeowner or landowner. It is important that private well water be tested regularly (at least 3 times per year) and that the well is maintained at all times. Well owners may also wish to install additional drinking water disinfection devices to ensure that the water supplied from their wells is safe to drink at all times.

What is an unprotected water source?

  • An unprotected water source refers to streams, rivers, cisterns, and poorly constructed wells, or any well that is not a drilled well and does not have a watertight casing that extends to a depth of at least six meters below ground level. The safety of well water may also be influenced by the original water quality in the watershed or catchment.
  • Unprotected water sources can easily become contaminated and unfit for drinking.

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What could happen if I drink contaminated water?

  • The health effects of drinking contaminated water can range from no physical impact to severe illness or even death.
  • Some of the effects of drinking contaminated water can be immediate, or not noticed for many years. These include gastrointestinal and stomach illnesses like:
    • nausea
    • vomiting
    • cramps
    • diarrhoea
  • Many factors affect the possible impact on health such as:
    • the age and general health status of the person
    • the type of contaminant
    • the amount
    • how long the person has been drinking the contaminated water

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What could the water be contaminated with?

Private wells can become contaminated with bacteria or chemicals such as nitrates.

  • Bacteria  - When a water test shows the presence of bacteria, it is considered unsafe to drink until the problem is fixed and the well is disinfected. The absence of bacteria in any one test does not ensure safety at other times. Regular testing throughout the year will establish your well water’s consistency and increase your confidence in its safety. Spring run-off, heavy rain events, or prolonged dry spells as well as wear and tear of the well structures or changes to the water catchment can all potentially affect the quality of your well water.
  • Total Coliforms  - Total coliform organisms are a group of bacteria that are commonly found in the environment, and are an indicator of the safety of your water. Total coliform bacteria, if present, indicate that disease-causing organisms (bacteria, viruses, parasites) could potentially be present in your water supply.
  • E. coli E. coli bacteria live only in the intestines of animals including humans. If any amount of E. coli bacteria is found in a water sample, it is an indication that human sewage or animal faeces has contaminated the water supply.
  • Nitrates - The presence of nitrates in well water is usually the result of farming activities like fertilizing, or seepage from septic systems. If nitrates are at levels above 10 milligrams per litre of water, an infant may suffer from a condition known as “blue baby syndrome” or methaemoglobinaemia. Blue baby syndrome is caused by the nitrates interfering with the blood’s ability to carry oxygen throughout the body.
  • Herbicides and Pesticides  - Herbicides and pesticides from both agricultural and household use can contaminate wells if used improperly or excessively. Always read and use the amount stated on the manufacturer's label.

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Is there a taste, smell, or colour to contaminated water?

Many times the contamination is odourless, colourless, and tasteless.

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What should I know about my water system?

  1. Know your watershed or catchment. Where does the water come from?
  2. Know your source (raw) water quality. How safe is the water that comes straight from your well before it enters any of your plumbing? Does it vary around the year?
  3. Only with all these components in place and assessed regularly throughout the year can you have increased confidence in the quality of your drinking water.
  4. Know your distribution system. Are piping and plumbing intact everywhere? Are there cross-connections or is there backflow potential? Might plumbing materials add contaminants such as lead to the water?

These can be complex questions. You may need to discuss them with your local public health inspector. To speak with a public health inspector, contact Halton Region.

Only with all these components in place and assessed annually can you have increased confidence in the quality of your drinking water year-round.

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How can I test my well water?

  1. Get a water bottle and submission slip from Halton Region Health Department. All materials and shipping are free .
  2. Remove the strainer screen from your household tap. Run the cold water through the tap for 3 - 5 minutes.
  3. Fill the bottle up to the indicator line directly from a household tap without rinsing the bottle or bottle cap. Be sure not to contaminate the bottle cap or spout while taking the sample.
  4. Fill out the submission slip. Provide your full address, including your postal code and telephone number, and other details required on the form.
  5. Return the water sample and submission form to your nearest Health Department water depot. The Health Department will send the sample by courier to the Ministry of Health Laboratory. Halton Region is not responsible for lost results.
  6. Water samples must be dropped off within 24 hours of being collected. The sample should be refrigerated unless it is dropped off immediately.
  7. There are three ways you can get the results of your well water test:
    1. The results will be mailed to you from the lab, 7 - 10 working days from the day the sample was submitted. An explanation of your results will be provided on the reverse side of the submission form.
    2. You can call the Ministry of Health Laboratory at 905-385-5379 for your test results after 3 - 5 business days from the day the sample was submitted. To call, you will need your PIN number. The PIN number is located on the side of the water sample bottle.
    3. You can pick up your results at the Ministry of Health Laboratory, 250 Fennell Avenue West, Hamilton (view mapExternal Link).

Halton Region is not responsible for lost results.

Other Tests - The Health Department will test water for nitrates free of charge. Please contact the Health Department to arrange for a nitrate test.

Although the Health Department does not offer testing for substances other than bacteria or nitrates, public health inspectors are available to advise you about other tests that may be done in relation to a specific health issue.

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