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revised April 08, 2014

Environmental Health

Protecting the public's health through risk assessment, enforcing standards, education and advocacy


Drinking Water

Private Wells

If you are a well owner, here are some important steps you should take to make sure your water is safe to drink. You can also pick up a free copy of the Well Water Information Kit from Service Peel – 7120 Hurontario St, Mississauga.

How could my well water become contaminated?

Contaminated well water has levels of bacteria and/or chemicals that can make you ill.
Contaminants can enter your well water if:     

  • The well is poorly maintained
  • Sewage or wastewater leaks from a septic system
  • Waste is put directly into the well
  • Fertilizers or pesticides are over-applied
  • Fuels and pesticides spill on the ground
  • A fuel storage tank leaks
  • Industrial solvents and chemicals are improperly handled

How do I test my well water?

Only a laboratory test can tell you whether your water is safe to drink. Since the quality of your water can change throughout the year, you should test your water regularly for chemical and bacterial contamination.

Peel Public Health can test your water for bacterial contamination. Pick up a water sample bottle from one of our pick-up locations or from any other public health unit. You should plan to collect your sample when you are sure you can deliver it to one of our drop-off locations within 24 hours. If your sample is left to sit for longer than this, the test results will not be accurate.

To collect a water sample, follow these steps:

  1. Remove all attachments from the faucet (tap), including the aerator or screen and any rubber washers. If you are unable to remove attachments, use a different indoor faucet to take your sample, but don’t use an outdoor faucet or garden hose.
  2. Disinfect the end of the faucet spout to remove debris and bacteria. You can do this by wiping it with an alcohol swab or by submerging it in a cup containing dilute bleach (1 part household bleach to 10 parts water). Don’t use a flame to disinfect it because this can damage the faucet.
  3. Turn on the cold water and let it run for two to three minutes. This removes standing water from your plumbing system.
  4. Remove the lid from the water sample bottle. To avoid contaminating the sample, do not touch the inside of the lid or bottle neck, put the lid down or rinse out the bottle.
  5. Fill the bottle to the line marked on the bottle, as shown in the instructions you received with the bottle.
  6. Close the lid firmly.
  7. Keep the sample cool, but not frozen, until you take it to the drop-off location. Remember to deliver the sample within 24 hours of collecting it, so the test results are accurate.

Where can I pick up bottles and drop off water samples?

Pick up water sample bottles

Location Hours of Operation
Service Peel
7120 Hurontario St.,
Mon - Fri
8 a.m. - 5 p.m.
Service Peel
10 Peel Centre Dr.,
Mon - Fri
8 a.m. - 5 p.m.
Cheltenham General Store
14387 Creditview Rd.,
During regular store hours.
Call 905-838-2729 for hours.
Town of Caledon
Administration Building
6311 Old Church Rd.,
Caledon East
Mon - Fri
8:30 a.m. - 4:30 p.m.

Drop off water samples for testing (within 24 hours of collection)

Location Hours of Operation
Service Peel
7120 Hurontario St.,
Mon - Thurs
8 a.m. - 4:30 p.m.
(Outside of these hours, use the
outdoor drop box.)
No drop-off on Fridays.
Town of Caledon
Administration Building
6311 Old Church Rd.,
Caledon East
Mon - Thurs
8:30 a.m. to 1:30 p.m.
No drop-off on Fridays
Ontario Central Public Health Lab
81 Resources Rd.,
Call 416-235-6556 or 1-877-604-4567 for hours.

What should I do if my well water is contaminated with bacteria?

STOP using it for drinking, brushing teeth and washing dishes if your water quality tests results show that your water is contaminated with bacteria. You could become ill if you drink it. Until you are able to fix the problem, use one of these sources of emergency drinking water:

Method Directions
Boiling Boil water for 5 minutes and allow to cool.
Chlorine Bleach Add 8 drops (1.25 mL or 1/4 tsp) per gallon (4.51 L) of water. Mix and let stand at least 15 minutes.
Bottled Use water from a reputable supplier. Make sure seal is not broken on bottle before use.

(Note: For chemically contaminated water, boiling and chlorine bleach cannot make it safe to drink. Use bottled water as a source of emergency drinking water.)

How do I disinfect a well contaminated with bacteria?

If your water is contaminated with bacteria, disinfecting it can make it safe again. Follow these disinfection instructions to fix a one-time case of bacterial contamination.

(Note: If there is an ongoing source of contamination or defect with your well, disinfection will not fix the problem. Find out how to maintain your well from the Well Water Information Kit, which you can pick up from Service Peel – 7120 Hurontario St., Mississauga.)

  1. Determine the amount of unscented chlorine bleach (5.25% solution) required for your well size. To do this, you need to:
    1. Measure the diameter of your well
    2. Measure the depth of the well and the resting water level, and then calculate the depth of the water
    3. Look up your well measurements in the table below to determine the amount of chlorine required for disinfection
    Volume of Bleach to Add for Every 3 Metres (10 Feet) of Water in the Well
    Casing Diameter Volume of Unscented Bleach
    (5.25% solution)
    Millimetres Inches Millilitres
    50 2 6
    100 4 30
    150 6 60
    200 8 100
    250 10 200
    300 12 250
    400 16 400
    500 20 650
    600 24 900
    900 36 2000 (2 litres)
    1200 48 3600 (3.6 litres)

    (Note: This table is for a 5.25% solution. If you are using a different solution, use Public Health Ontario's online dilution calculator to determine the amount you need.)

  2. Pour this amount of unscented chlorine bleach into the well.
  3. If possible, mix the water in the well. To do this you need to attach a hose to a tap and run water through the hose and back into the well.
  4. Remove or bypass any carbon filters that are in the system for water treatment. This ensures that the chlorine you have added does not get removed.
    (Note: After this disinfection process, replace these with new filters because the old filters could reintroduce bacteria into the system.)
  5. Run water from every faucet in the house, until you can smell a strong odour from the chlorine. If there is no chlorine odour, or if it is very weak, add more chlorine bleach to the well and run water from every faucet until you do smell the chlorine.
    (Note: Avoid adding too much chlorine into the septic system because this may kill the bacteria needed for septic decomposition.)
  6. Drain your water heater. Fill it with the chlorinated water.
  7. Backflush (make the water flow backwards) the water softener and all water filters, but not the carbon filters.
  8. Leave the chlorinated water to stand in the system for at least 12 hours.
    (Note: The water is not safe to drink at this time. Use either an alternative source or the boiled well water you set aside before disinfection.)
  9. Clear the chlorine from the well. To do this, run an outside hose to the ground surface, and then run clear water through the faucets. You will know the chlorine is cleared when there is no longer an odour from the chlorine.

After you have disinfected the well, test it again for contamination. Do not drink it without boiling it until the test confirms it is safe to drink.

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Revised: April 08, 2014


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