Well water and health: Test your well water

Why, when and how you should test your well water, and what contaminants you should test for.

Why you should test your water

As a private well owner, you're responsible for monitoring and maintaining your water quality. Testing your well water quality ensures that it doesn't contain microbial or chemical contaminants that can negatively affect your health.

Microbial contaminants include pathogenic microorganisms. These are extremely small organisms that may cause disease, and include:

viruses
bacteria
protozoa

Chemical contaminants can be naturally occurring due to the types of rocks and minerals found in and near your aquifer, or because of human activity. This can include:

heavy metals
trace elements
common minerals

Consuming or using water that has contaminants above the acceptable limits in the Guidelines for Canadian Drinking Water Quality may affect your health.

Many contaminants won't affect the smell, taste or colour of your drinking water.
Even if your water seems fine, you can't know for sure without testing. Testing is especially important if people who rely on the well water include those who are:

seniors
infants
nursing
children
pregnant
immunocompromised

These people are often more vulnerable to contaminants than others.

When to test your water

Test your well water at least once every 6 months for microbial contamination. Testing for chemical contaminants varies depending on the contaminant. Check with your local public health authorities about how often to test for specific chemicals in your area. General water quality parameters should be tested once every 2 years.

The best time to sample your well water is when there is the greatest chance of contamination, such as:

in early spring and fall
after a fire or wildfire
after heavy rains or floods
after a long dry spell or drought
after the well hasn't been used for a long time

You should also test your water when:

there are changes in land use or activities near your well
you notice a change in the colour, taste or smell of your water
you complete repairs or maintenance to your well or related equipment

You may need to test more frequently if your well is vulnerable to contamination.

Your well may be more easily contaminated if it's:

dug
in bedrock
has only a thin layer of soil over it
shallow (less than 25 metres of casing)

The quality of the groundwater is directly influenced by its surrounding environment. The water quality can change depending on factors such as weather and land use. This is especially true for drinking water wells where surface waters can quickly reach the groundwater without being properly filtered by the particles in the ground.

Regular testing will help you keep track of changes in your water quality over time.

How to test your water

Your provincial or territorial drinking water authority or your local public health unit can help you find an accredited laboratory to do the tests. Only tests done through an accredited laboratory or your local public health unit will be accurate and reliable.

Reliable and accurate results also depend on following all instructions from the accredited laboratory on:

collecting the water sample
labeling and storing the water sample
completing and submitting the test forms
handling and transporting the water sample to the laboratory

Provincial and territorial resources

Testing for microbial contaminants

Microbial tests usually look for E. coli and total coliforms. These are bacteria that indicate whether there may be other, disease-causing microorganisms in your water.

Table 1: Testing for *E. coli*
Test for:	Bacteria: E. coli and total coliforms
Where it comes from:	E.coli comes from human and animal feces. Possible sources include nearby: feedlots septic systems manure storage or spreading Total coliform bacteria can be found in soil, on vegetation, and in feces. They may be carried to your well with: rain melting snow surface water
How often:	Every 6 months, or more frequently.
Acceptable level:	No E.coli in a 100 ml sample of water. No total coliforms in a 100 ml sample of water.
What your test results mean:	If your well water sample contains any E. coli, the water is not safe to drink. If your well water sample contains any total coliform bacteria, your water might not be safe to drink. More information is needed.
What to do:	If E. coli or total coliform bacteria are found in your well water sample: Collect and test another water sample as soon as possible to confirm whether your water is contaminated with E. coli, total coliforms or both. If the second test doesn't show any contamination, test a third sample to confirm this result. If the second or third test confirms that your well water is contaminated, shock disinfect your well and take corrective actions. Treat your well for contaminants If there's E. coli in your well water sample: boil any water used for drinking, cooking or teeth brushing or use another safe source of water until test results show that the water is safe to drink If there is total coliform bacteria in your well water sample: you can continue to use your drinking water while you wait for further test results.

If you or a family member have a gastrointestinal illness and suspect that it's related to drinking your well water:

speak to your doctor and local health unit
have your water tested

Testing for chemical contaminants

Canadian well water can contain chemical contaminates that may adversely affect your health if they're above drinking water guideline values. For many chemicals, you need to be exposed over several years for health issues to occur. If a chemical exceeds an acceptable level, it will need:

additional sampling
appropriate corrective actions

Contact your local public health unit or drinking water authority for information on chemical contaminants that are of concern in your area.

Guidelines for Canadian Drinking Water Quality

Table 2: The most common chemicals to test for
Contaminant	Common sources	Main health concerns
Arsenic	Naturally occurring in some areas Mining activities Industrial effluents	Increased risk of cancer (lung, bladder, liver, skin) Skin, vascular and neurological effects (numbness and tingling of extremities)
Copper	Naturally occurring in some areas Agricultural activities Mining activities Copper pipes and plumbing system components made with copper	Although copper is essential for humans, high levels of copper can cause gastrointestinal upsets and may impact the liver and kidney
Lead	Plumbing components made with lead and galvanized steel pipes, especially if your water is corrosive. Note: all dug wells are at high risk of having corrosive groundwater	Reduced intelligence in children Behavioural effects in children Increased blood pressure and renal dysfunction in adults Probable carcinogen
Manganese	Naturally occurring in some areas Industrial discharge Mining activities Leaching from landfills	Neurological development and behaviour Deficits in memory, attention and motor skills Formula-fed infants may be especially at risk
Nitrate and nitrite	Naturally occurring in some areas Agricultural activities Domestic sewage	Methaemoglobinaemia (blue baby syndrome) Effects on thyroid gland function in bottle-fed infants Short exposures above the guidelines can cause illness
Uranium	Naturally occurring in some areas Industrial contamination Nuclear industry emissions Mining activities Phosphate fertilizers	Damage to kidneys and bones

You may need to test for other chemicals depending on the situation.

Volatile and semi-volatile compounds may be a concern if, for example:

your well or property has been damaged by fires
a fuel spill has occurred nearby (such as a leaking oil tank used for home heating)

You can be exposed to these compounds by breathing them in or absorbing them while bathing or showering, in addition to consuming them.

Heavy metals, hydrocarbons, pesticides or per- and polyfluorinated substances may be a concern if you're in close proximity to:

industrial sites
agricultural sites
contaminated sites

If your well is in an area that's at high risk of contamination, you may need to:

test more frequently
look for suitable treatment options

Contact your local public health unit or drinking water authority to find out if you should test for these or other chemicals.

Testing for general water quality

You should also test for general water quality. This includes:

pH
iron
chloride
alkalinity
ammonia
hardness
sodium sulphate
total dissolved solids
dissolved organic carbon

The acceptable levels for these parameters are based on aesthetic or operational objectives instead of health. They aren't harmful, but may affect your well water's:

taste
smell
colour

They can also interfere with the operation of your plumbing, appliances or any treatment that you may want to install.

Although iron is generally considered an aesthetic issue, iron adsorbs metals such as lead, arsenic and manganese. Adsorption is when particles stick to a surface and are held there by physical or chemical forces. For this reason, removing iron is a good first step in reducing the level of these metals in drinking water.

If any of these parameters are above their aesthetic or operational objective levels, you may safely continue to drink and use your water. You may choose to treat your water to prevent common problems such as staining or scaling, or to improve the taste or smell of your water.

Water quality test results

Your water quality test results will tell you which contaminants are present in your well water and at what concentration.

If there are contaminants in your water above the recommended guideline values, take corrective action as soon as possible.

Treat your well for contaminants

Some provinces and territories have online resources that can help you interpret your water test results. Alternatively, contact your local public health unit or drinking water authority for more information.

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Date modified:: 2024-08-02

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