Well Water Testing

Almost half the population of Wellington and Dufferin Counties gets their drinking water from private wells. To help ensure water is safe, Public Health Ontario offers water-quality testing for bacteria. We recommend you test your well water for bacteria at least three times a year, with the most important time to test being the spring. Public Health can help you interpret your test results as well as provide information on disinfection and filtration systems, well upgrading and maintenance.

How to get your well water tested

1. Pick up an empty water sampling bottle with attached form from one of the locations below or a municipal office (please call your municipal office to find out if they participate in this program).

2. Follow the instructions provided with the sampling bottle to take your sample and fully complete the form that accompanies the bottle.

3. Drop off the sample at one of the locations listed below. The drop-off times below ensure your sample makes it to the testing lab in Hamilton on time.

Drop-off times for well water testing


When to bring sample in

Guelph Public Health Office

160 Chancellors Way

Monday to Thursday: 8:30 a.m.-4:30 p.m.
Friday: 8:30 a.m.-11:00 a.m.

Closed on holidays.

Fergus Public Health Office

490 Charles Allen Way

Monday to Thursday: 8:30 a.m.-4:30 p.m.
Friday: 8:30-10:30 a.m.

Closed on holidays.

Orangeville Public Health Office

180 Broadway

Monday to Thursday: 8:30 a.m.-4:30 p.m.
Friday: 8:30-10 a.m.

Closed on holidays.


Mel Lloyd Centre, 167 Centre Street

Monday and Wednesday: 8:30-11:30 a.m.

Closed on holidays.

4. We send your water samples to Public Health Ontario laboratory for E. coli and total coliform testing. 

5. Get your results and see what they mean.

6. Public health inspectors can help you interpret the results of your water test. Call 1-800-265-7293 ext. 4753.

If you need further testing (e.g., for nitrates, sodium, fluoride, metals, chemicals), you must contact a private laboratory. Find one in this list of accredited laboratories or call us at 1-800-265-7293 ext. 4753.

How to disinfect your well

If your lab result shows that your water is unsafe, you will need to disinfect your well. It’s most convenient to treat your well in the evening as you will not be able to use the well for at least 12 hours.

  1. Draw enough water for overnight use.
  2. Bypass treatment devices if you have them.
  3. Make disinfectant by mixing chlorine/household bleach with several litres of water. Be sure to use household bleach purchased within the last few months since its strength will decrease over time.
Bleach and water to add to disinfect your well based on type of well

Type of well

Amounts of chlorine/household bleach and water

Dug well

For every 1.5 m (5 ft.) of well water depth, mix 1 L of household bleach with several litres of water to make a disinfectant.
Drilled well For every 7.5 m (25 ft.) of well water depth, mix 170 mL of household bleach with several litres of water to make a disinfectant.
Dug/drilled wells of unknown depth Mix 2 L of household bleach with several litres of water to make a disinfectant.
  1. Pour the disinfectant down your well. The vent hole in a drilled well may be a good place to pour in the disinfectant.
  2. Turn on each tap—inside and outside your house—one at a time. Let the water run until you smell a strong odour of chlorine. If you can’t smell chlorine, add more to the well.
  3. Let the chlorinated water stay in the plumbing system for at least 12 hours. Do not run any water at this time.
  4. Starting from outside, flush the system to remove chlorine one tap at a time. This order will reduce the load on your septic system.
  5. Let each faucet run until there is no longer a strong odour of chlorine.
  6. Wait a minimum of 48 hours and sample again.

Avoid contamination: Take care of your well

Make sure the:

  • Well cap fits tightly and is in good condition
  • Well head is clear of brush, debris and other obstructions
  • Casing is at least 40 cm (16 in.) above the ground
  • Joints, cracks and connections in the well casing are sealed
  • Vent openings are facing down and screened to keep insects and mice out
  • Ground is mounded around the well casing to divert water away