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Well water testing in Ontario: what to test, when, and what’s free

If your water comes from a private well or cistern, testing it is up to you.⁠[1] Public Health Ontario tests it for bacteria (E. coli and total coliforms) for free, using a free well water test kit (a sample bottle) you pick up locally.⁠[2] That free kit does not test for chemicals such as nitrate, arsenic or lead. Those need a licensed lab. Hamilton Public Health and Halton Region both recommend testing for bacteria at least three times a year.⁠[3][4]

Updated November 4, 2026
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What to test in well water: free test or lab test?

Free bacteria test Licensed lab test
Who runs it Public Health Ontario A lab licensed by the Province
What it checks E. coli and total coliforms Chemicals and minerals you choose: for example nitrate, arsenic, fluoride, lead, sodium
Cost Free The lab sets its price; call and ask
Who can use it Private wells, cisterns and treated lake water. Untreated lake, stream or pond water is not accepted. Anyone
Results Online in 2 to 4 business days Ask the lab

Sources: Public Health Ontario⁠[2]; Government of Ontario⁠[1]; City of Hamilton⁠[3]; York Region.⁠[5] Find a lab on Ontario’s list of licensed laboratories.

Clear, good-tasting water can still contain harmful bacteria, Public Health Ontario says, which is why testing matters even when nothing seems wrong.⁠[2]

How the free bacteria test works

  1. Get a sample bottle from your local public health unit or a pick-up spot it lists. Some units, such as Halton, also mail bottles.⁠[4]
  2. Collect the sample from an indoor tap, following the instructions with the bottle exactly.
  3. Keep it cold, in the fridge or on ice.
  4. Register the sample on Public Health Ontario’s online water testing portal, or fill in the paper form in the kit. Keep your barcode.⁠[3]
  5. Drop it off quickly. In Hamilton, samples must be tested within 48 hours of collection; Halton asks for drop-off within 24 hours.
  6. Get your results online in 2 to 4 business days, using your barcode and last name.⁠[2]

If you have a treatment device, Hamilton Public Health suggests two samples: one from your drinking tap and one from before the treatment, so you learn about both your tap water and your source.⁠[3]

In Hamilton

Kits are available at Municipal Service Centres, City Hall, the Public Health Ontario Laboratory and several rural stores and post offices. See water testing in Hamilton for every pick-up and drop-off location and the best days to drop off.

What does a coliform or E. coli result mean?

Ontario groups results into three levels (counts per 100 mL of water):⁠[1]

Result What Ontario says What to do
Total coliform 5 or less, and no E. coli No significant evidence of bacterial contamination Keep testing regularly to see how stable your water is
Total coliform more than 5, and no E. coli Significant evidence of bacterial contamination. May be unsafe to drink. Contact your local public health unit as soon as possible
Any E. coli Unsafe to drink. Evidence of animal or human waste. Stop drinking the water. Contact your public health unit immediately.

Total coliforms are bacteria found in animal waste, sewage, soil and plants; finding them may mean surface water is getting into your well. E. coli comes from the gut of people and animals, so finding it points to animal or human waste.⁠[1]

What would cause a well water test to fail? Ontario lists surface water getting into the well, a cracked cap or casing, ponding around the well, flooding, and nearby sources of contamination.⁠[1] If your result is unsafe:

  1. Stop drinking it. Use bottled water or another safe supply, and call your public health unit.
  2. Inspect the well: cap, seal and casing, and keep the area around it clear and sloped away.
  3. Shock chlorinate the well and your plumbing. See Ontario’s fact sheet, Disinfecting private water wells.
  4. Test again. Halton suggests retesting after you disinfect.⁠[4]
  5. If problems keep coming back, have a licensed well contractor inspect the well.

Ontario says boiling water at a rolling boil for at least one minute kills harmful organisms, but does not remove most dissolved contaminants.⁠[1] York Region adds that boiling makes chemicals more concentrated.⁠[5]

In Hamilton, a public health inspector can help you read your result: 905-546-2189.

What the free test doesn’t cover

The free test only looks for bacteria. Ontario says a clean bacteria result tells you nothing about chemicals, which come from natural minerals in the rock or from spills.⁠[1] Public Health Ontario labs no longer test well water for nitrate or sodium.⁠[5]

Common concerns Ontario lists for wells:⁠[1]

Concern Usual cause What Ontario says about it
Nitrate Fertilizer and septic systems A health risk for infants above 10 ppm
Arsenic, uranium, radium Natural minerals; industrial spills Long-term health risk
Fluoride Natural minerals Can mottle children’s adult teeth in severe cases
Iron, manganese Natural minerals Stains and cloudy water; not a health problem
Salt (sodium) Natural minerals; road salt Unpleasant taste
Fuels, pesticides Spills, old tanks, spraying Long-term health risk

Test for these through a licensed lab. Ontario says to test when you notice a change in taste, colour or smell.⁠[1] Some regions add local options: the Region of Waterloo tests well water for nitrate and fluoride for a fee, and recommends those tests once a year.⁠[6]

How often should you test well water?

Who Advice
Hamilton Public Health Bacteria at least three times a year. Not tested in over a year? Take three samples at least a week apart.
Hamilton Public Health, cisterns Bacteria at least four times a year
Halton Region At least three times a year (spring, summer, fall), plus after flooding, heavy rain or snow melt, after you disinfect, and after nearby construction or septic work
Region of Waterloo Bacteria three times a year; nitrate and fluoride once a year
Public Health Ontario Regularly, and especially after spring thaw, heavy rain, flooding or well maintenance

Public Health Ontario says testing matters most for households with young children, older adults, or anyone with a weakened immune system.⁠[2] In Hamilton, about 28% of samples from private wells and cisterns had unsafe levels of bacteria in 2023.⁠[3]

Lead from the rock: Hamilton’s escarpment wells

In 2006, Hamilton Public Health Services issued an advisory to rural residents above the Niagara Escarpment who drink from a drilled well.⁠[7] Lead occurs naturally in the bedrock there, in spotty, unpredictable patterns, and some wells have lead above Ontario’s standard. When Public Health tested 45 drilled wells in northwestern rural Hamilton, 13 were over the standard. The City says it is not possible to predict which wells are affected.

The Medical Officer of Health advises these well owners to:⁠[7]

  • Test for total and dissolved lead through a licensed lab (see how to test for lead).
  • Test in late fall, after the leaves have fallen, or in early spring. Do not test in summer, when lead is likely to be lowest or not detectable.
  • Test before treating the water.
  • Know that if the lead comes from the groundwater, flushing will not get rid of it.

The City lists these options if lead is found: bottled water, water from a known safe supplier, a reverse osmosis system, a distiller, or a filter labelled “NSF/ANSI-53 for lead removal”.⁠[7] The City says homes on urban municipal water, on the Carlisle, Freelton, Greensville or Lynden systems, or on a rural cistern do not need this bedrock test.

What your lead number means: lead test results. Filters for lead: water filters for lead.

Other local advisories

Area Advisory Source
Hamilton, above the escarpment Natural lead in some drilled wells (above) City of Hamilton
Hamilton, two rural areas Public Health found arsenic above the provincial standard in one well near Sulphur Springs Road and Governors Road, and one in the Trinity Church Road and Tisdale Road area, south of Kirk and Chippewa Roads to Hall Road. It advises well owners in these areas to consider testing for arsenic. City of Hamilton
Hamilton, near John C. Munro Airport PFOS was investigated. The City says exposure through well water is believed to be unlikely and that bacteria is a much higher risk; test for bacteria. City of Hamilton
Other areas Ask your local public health unit. We add advisories as we cover more cities.

Radon in well water

Health Canada says radon in drinking water is usually not a problem, and the bigger health risk is radon in indoor air.⁠[8] It also says radioactive elements in water tend to be higher in groundwater than in lake or river water. To know whether radon is a problem in your home, Health Canada says to test the air.

Treating well water

Ontario says no single treatment works for everything, and each system must be installed and maintained as the maker directs.⁠[1] Test first so you know what you’re treating. For lead, see water filters for lead. For hardness, see hard water. For bacteria problems, start with shock chlorination and your public health unit.

Who to call

  • Your local public health unit, for bottles and help reading results. In Hamilton: 905-546-2189.
  • Ontario’s Wells Help Desk, for well construction and the Wells Regulation: 1-888-396-9355.⁠[1]
  • Hamilton well systems and hardness: see Hamilton tap water.

Sources

  1. Government of Ontario, Testing and treating private water wells. Checked . ↩︎
  2. Public Health Ontario, News release, June 3, 2026. Checked . ↩︎
  3. City of Hamilton, Well Maintenance and Water Testing. Checked . ↩︎
  4. Halton Region, Testing your well water. Checked . ↩︎
  5. York Region, Private Well Water Testing. Checked . ↩︎
  6. Region of Waterloo, Small Drinking Water Systems and Private Wells. Checked . ↩︎
  7. City of Hamilton, Naturally Occurring Lead in Bedrock. Checked . ↩︎
  8. Health Canada, Water Talk: Radionuclides in drinking water. Checked . ↩︎