Private Wells

Taking a water sample

Test your drinking water for the presence of harmful bacteria at least three times a year.

Step 1

Use a water sample bottle with attached form. You can get these from the Health Department or Ontario Ministry of Health and Long-Term Care Public Health Laboratory.

Step 2

Remove all attachments from the faucet including the aerator, rubber washer and any hoses.

Step 3

Be sure to disinfect the tap with alcohol or plain bleach (5.25 per cent sodium hypochlorite).

Step 4

Run cold water tap for a minimum of five minutes.

Step 5

Unscrew cap from water sample bottle. Be sure not to contaminate the inside of the cap or the neck of the sample bottle with your fingers.

Step 6

Fill bottle to 200 mL water line indicated on bottle.

Step 7

Screw cap on tightly.

Step 8

Fill out the form that is comes with the water sample bottle.

Remember to write the PIN on the form so you can get your results over the phone.

Step 9

Put bottle filled with water sample inside an insulated cooler with ice pack and take everything to the nearest drop-off location.

Note: All laboratories must receive water samples within 24 hours of the sampling date. Samples received after 24 hours will not be tested.

What should I do if I suspect my well water is not safe?

• Stop using the well water and contact the Durham Health Connection Line.
• Use an alternate source of potable water (e.g. boiled water, commercially bottled water) for drinking and cooking.
• Do a visual check of your well (See the Homeowners well maintenance and inspection checklist).
• Where applicable, check the operation of installed treatment equipment (e.g. UV light).
• Consider well disinfection or the installation of long term treatment options.
• Call a licensed well technician or water treatment specialist.

If only bacteriological contamination is present and you want to continue using the water from your well, bring water to a rapid rolling boil for at least one minute and let it cool before using it for drinking, making infant formula, juices, ice or recipes, brushing your teeth, rinsing contact lenses, and washing food or dishes. Refrigerate your boiled water until it is finished. Also see Facts About ... Boil water advisories for additional information.

Note: If chemical contamination (e.g. pesticides, oil, gasoline, etc.) of your well water supply is suspected, do not boil your drinking water. Contact the Durham Health Connection Line for further advice.

Blue-green algae are microscopic bacteria that occur naturally in freshwater lakes, ponds, rivers and streams. During warmer weather periods (typically June to October), blue-green algae blooms may occur in nutrient rich and slow moving or stagnating waters. Blue-green algae can appear in various forms where water appears discolored or where foam, scum or mats of algae are present. Water may look soupy or have a paint-like film on the surface. The colour of the algae are often blue-green, but may also be olive-green or red.

Fresh blue-green algal blooms often smell like fresh cut grass, while older blooms can smell like rotting garbage. Older blooms are more likely to release toxins as the cells die off.

Blue-green algae blooms may contain toxins known as microcystins, a specific cyanotoxin with known health effects that can be harmful to the health of you and your animals.

Municipal drinking water systems

Municipal drinking water systems that use surface water sources are routinely monitored for blue-green algae and microcystin. In addition to visual monitoring of the lake and intake lines, both the raw water and treated water are assessed.

Durham Region water treatment plants have complex treatment systems capable of removing blue-green algae and their toxins. The risk of exposure of cyanotoxins from municipal drinking water is extremely low.

In the event microcystin test results for treated water exceed the Ontario Drinking Water Quality Standard, residents will be immediately notified.

Private drinking water systems

Homeowners are encouraged to visually monitor surface waters (e.g. lakes, rivers, streams) that are used as drinking water supplies for the presence of blue-green algae blooms between the months of June and October. When a bloom condition is present, residents who draw water from a nearshore well or directly from affected water bodies are advised not to drink or bathe in contaminated water.

Home water treatment systems may not be capable of removing toxins from the water supply. Consult with a water treatment specialist before selecting and installing a residential scale treatment system.

Health effects

Exposure to harmful microcystins through drinking water poses a health risk to everyone. Children six years of age and younger are most at risk for severe illness (e.g. liver damage).

If swallowed, contact with microcystins can produce the following negative health effects:

• Small quantities - headaches, fever, diarrhea, abdominal pain, nausea and vomiting.
• Large quantities - more serious health effects may occur such as liver damage.

You are advised to seek medical attention if you experience any of the above symptoms during a blue-green algae bloom event.

Precautions

If a blue-green algae bloom is identified by the Health Department and elevated levels of microcystin are confirmed by water quality testing, the public will be notified of any advisories or warnings issued. Precautionary measures include the following actions:

• Do not use the water for drinking, food preparation or making infant formula.
• Do not boil the water. Toxins are not destroyed by boiling and may actually increase toxin levels.
• Do not manually treat the water with chlorine, herbicides, copper sulphate or other algaecides that may break open algae cells and release toxins into the water.
• Do not rely on a jug filtration system, as it will not remove the toxins.
• Use an alternate source of potable drinking water, such as commercially bottled water for the duration of the bloom and for several days after a bloom dissipates.
• Bathing or showering with water affected by a blue-green algae bloom is not recommended.

Learn more about blue-green algae.

To report blue-green algal blooms, call the Ministry of the Environment Conservation and Parks (MECP) Spills Action Centre at 1-866-MOE-TIPS (663-8477), or call the Durham Health Connection Line.

To disinfect your well you should shock chlorinate the system with a high concentration of bleach.

Protect your skin from splashes from the bleach by using gloves, goggles and clothing. Never mix bleach with other chemicals.

• Follow the chart included in the Private Well Water Manual under the shock chilorination section for correct measurements.
• Regular household bleach (Sodium Hypochlorite 5.25 per cent) should be used to chlorinate your well. Do not use "fresh scent" bleach or other products to disinfect wells.

Be sure you have another safe, potable source of water to use during this process.

Wells require maintenance as they age. Use the Homeowners well maintenance and inspection checklist to regularly inspect your well.

Warning: Do not enter a well or well pit at any time during an inspection.

You should think about properly abandoning or plugging your well if:

• A new well is drilled and you are no longer using the old well.
• The water quality is bad and you need another water supply.

An Ontario Ministry of the Environment Conservation and Parks (MECP) licensed well contractor must be hired to abandon the well.

*Source: Best Management Practices: Water Wells (Ontario Ministry of Agriculture, Food and Rural Affairs/Agriculture and Agri-Food Canada)

• Facts About... Boil water advisories
• Facts About... Barium in well water
• Facts About... Lead in drinking water
• Drinking Water Indicator Bacteria and Their Significance, Public Health Ontario, October 2022