Sample date: April 18, 2015

Sunny. Wind north 30 km/h gusting to 50. High 19 except 12 near Lake Erie. UV index 7 or high.


Environment Canada
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Safe Water

Elevated Fluoride Levels in Drinking Water

Small Drinking Water Systems

Well Water Safety

This page was reviewed or revised on Tuesday, September 17, 2013 9:22 AM


Why Should You Sample Your Well?
How To Sample Your Well For Bacteria
Water Quality Tests
Drinking Water Results
How To Disinfect Your Well
Bottled Water
How To Care For Your Private Well
Water Treatment Devices For Bacteria
Water Treatment Devices For Chemicals
How To Prevent Contamination
External Links

Why Should You Sample Your Well?

Drinking water that has harmful bacteria can make you sick. These bacteria can give you stomach cramps and/or diarrhea, as well as other problems. Water that has these bacteria is unsafe to drink!

The only way to make sure your water supply is safe to drink is to test it regularly. Testing for bacteria is done FREE.

Water testing kits are available at Lambton Public Health, 160 Exmouth St., Point Edward as well as the following locations:

North Lambton Community Health Centre (reception)
59 King St. W., Forest
Tuesday & Thursday 12:30 p.m.-1 p.m.

Lambton Public Health Forest sub-office (basement)
59 King St. W., Forest
Tuesday & Thursday 1 p.m.-2 p.m.


CEEH of Bluewater Health. Hospital lab (basement)
450 Blanche St., Petrolia
Monday to Thursday 8 a.m.-2:00 p.m.

How often to sample:

Dug Wells - at least 3 times per year.
Drilled Wells - at least 3 times per year.
Well Points - at least 3 times per year.

Sampling your water supply at least 3 times per year for bacteria is recommended. The best times to sample are: spring (after the snow melts), summer and fall. If you notice a change in the taste, odour, colour or clarity of the water, additional samples should be taken. Regular sampling and maintenance of your drinking water system will ensure your water is safe to drink.

We also recommend that you have your well water tested for nitrates.

How to Sample Your Well for Bacteria

Sampling Procedures

  1. Obtain a 200 ml water sample bottle from your Health Unit or Public Health Laboratory.
  2. Remove aerators and other attachments from your tap.
  3. Disinfect around the inside of the nozzle with a flame from a match or lighter. If nozzle is plastic, swab with chlorine bleach.
  4. Let water run for 2-3 minutes before taking the water sample.
    • Do not touch the bottle lip and do not rinse out the bottle.
  5. Fill bottle to the "fill line" directly from the tap without changing the flow of water.
  6. Replace cap tightly.

    • Complete "Bacterial Analysis of Water" form, which is attached to water bottle.

Returning Your Sample

  1. Samples should be refrigerated after collection.
  2. You should collect your sample on the day you deliver it to the Health Unit.
  3. Sample and all forms must be submitted within 24 hours of collection.

Water Quality Tests

Total Coliforms

  • This group of bacteria is always present in animal wastes and sewage, but is also found in soil and on vegetation.
  • The presence of these bacteria in your wells is usually the result of soil run-off or septic tank seepage.

Escherichia Coli (E. Coli)

  • These bacteria are only found in the intestines of people and animals.
  • The presence of E. coli bacteria in your well is usually the result of recent sewage contamination from a nearby source.
  • These bacteria are the ones that may cause disease.


  • Nitrates are the end result of a chemical reaction, they are not bacteria.
  • The presence of nitrates in your well water is usually the result of farming activities like fertilizing or seepage from septic tanks.
  • Infants less than six months old can become sick from drinking formula mixed with water high in nitrates. The nitrates in the formula reduce the amount of oxygen carried by the blood and can cause "blue-baby syndrome" (methaemoglobinemia).

Drinking Water Results

Total Coliforms

E. coli

What It Means



Safe for drinking. Maintain regular testing.



One sample with this result is unsatisfactory. Resample.



Satisfactory if this range is achieved for 3 samples taken 1-3 weeks apart.

6 to > 80


Unsafe for drinking unless boiled or treated.

1 to > 80

1 to > 60

Unsafe for drinking unless boiled or treated.


  Unsafe for drinking unless boiled or treated.


  Unsafe for drinking unless boiled or treated.

If your results are unsatisfactory:

  • Refer to "How to Disinfect Your Well"
  • Resample

 Do not drink the water until you receive satisfactory sample results.

If bacteria are present in your well, call Lambton Public Health at 519 383-8331 or toll free 1-800-667-1839 and talk with a Public Health Inspector about the operation of your well.

How to Disinfect Your Well

Well water supplies can be disinfected by adding the following amounts of chlorinated household bleach:

Dug Wells

3 ft. (1 m) diameter, add two gallons (8 liters) of household bleach for every 10 ft. (3m).

Drilled Wells

6" (15 cm) diameter, add 7 ounces (220 ml) of household bleach for every 10 ft. (3 m).

Well Points

2" (5 cm) diameter, add 1 ounce (29 ml) of household bleach for every 10 ft. (3 m) of depth.

Procedure To Follow

  1. Add household bleach to the well. If you don’t know how high the water stands in a drilled well, use the well depth to estimate how much household bleach to add.
  2. Remove or by-pass any carbon filter on the system.
  3. Run water through all taps until you can smell chlorine and then turn the taps off. This will thoroughly chlorinate all plumbing fixtures. Allow chlorine solution to sit at least 12 hours.
  4. Pump the water to waste through an outside hose until no further odour of chlorine can be detected. Do not allow the chlorinated water into the septic tank as this will kill bacteria essential to the septic tank operation.
  5. When smell of chlorine is gone, stop running water and wait 48 hours before bringing in another sample for testing.

Emergency Treatment

Remember you’re disinfecting your well because the water is unsafe. You can make the water safe by:

  1. Boiling it for 1 minute.
  2. Adding 8 drops (1.25 ml or ¼ teaspoon) of chlorinated household bleach per gallon (4.5 L) of water, mixing it well and allowing it to stand for 15 minutes.

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 Canadian Food Inspection Agency makes spot checks from time to time of both domestic and foreign bottled water.

Municipal water supplies are checked for 100 or more substances. In bottled water, only three substances must be checked. They are bacteria content, fluoride and total dissolved solids (magnesium, iron, sodium).

Bottled water contains naturally occurring bacteria, which under improper and/or prolonged storage conditions, can 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.


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

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 are 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.

Cistern water should be used only for lawn and garden watering, washing cars, etc.

The use of cistern supply for bathing or human consumption is not recommended.

How to Care for Your Private Well

Your well 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.

 Make sure that:

  • Sanitary seal or well cap is securely in place and water-tight.
  • Cap is at least 12 inches above the ground.
  • Joints, cracks and connections in the well casing are sealed.
  • Surface draining 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 should be investigated immediately.

Water Treatment Devices for Bacteria


  • Mechanical units that continuously add chlorine to the water storage tank.
  • Chlorine in the tank is allowed enough contact time to kill harmful bacteria.
  • Requires continuous checking to make sure that the right amount of chlorine is added to water.

Ultra-Violet Light:

  • Water is passed through an ultra-violet light source to kill harmful bacteria.
  • Water should be filtered before treatment.
  • Water for drinking should be refrigerated after treatment.


  • Devices that boil water in one compartment, condenses the vapour and then collects it in another.
  • Water should be filtered before treatment and refrigerated after treatment.
  • Removes some organic and inorganic chemicals.


  • Mechanical units that add small amounts of ozone to the water.
  • Ozone kills most harmful bacteria.
  • Water for drinking should be refrigerated after treatment.

Water Treatment Devices for Chemicals

Carbon Filters (Does not kill bacteria):

  • Removes some chemicals by passing the water through an activated carbon filter.
  • Best at removing tastes, odours and organic chemicals.
  • Filters must be changed according to the manufacturer’s instructions.

Reverse Osmosis (Does not kill bacteria):

  • Removes some chemicals by passing water through a semi-permeable membrane.
  • Best at removing inorganic chemicals (nitrates).
  • Often used in combination with carbon filters.

How to Prevent Contamination

  • Do not allow liquids or wastes from garbage and manure piles to drain towards the well casing.
  • Do not treat the area around the well with pesticides or fertilizers.
  • Do not flush oils, detergents, paints, solvents or other chemicals down the toilet.
  • Chlorinate and test your well after any repairs.

Abandoned wells should be carefully sealed to prevent pollution of ground water and any safety hazards. Consult with your local Ministry of Environment & Energy office. The hiring of a well contractor qualified to seal wells is strongly recommended.

External Links:

Well Aware

Adapted from the original produced by The Waterloo Regional Health Unit.

For further information on well water quality contact a Public Health Inspector at the Lambton Public Health