Question 1

How often should I test my well in Ontario?

Accepted Answer

Ontario's Ministry of Health (MOH) recommends testing private wells for bacteria — specifically E. coli and total coliform — at least twice per year, with spring and fall being the highest-risk periods due to snowmelt runoff and seasonal groundwater fluctuation. Chemical parameters such as arsenic, nitrates, sodium, hardness, and iron should be tested every 3–5 years, or immediately following any change in water taste, odour, or appearance; after nearby agricultural activity or spills; after a period of flooding; or after any well maintenance or pump work. Annual testing is advisable for wells near agricultural operations or septic systems.

Question 2

What contaminants are most common in Ontario wells?

Accepted Answer

In the rural and semi-rural areas served by private wells around Ontario and across Ontario, the most common water quality concerns are: total coliform bacteria and E. coli from proximity to septic systems or agricultural runoff; nitrates from fertilizer application and manure — particularly dangerous for infants under six months; naturally occurring arsenic from Ontario's geological formations, which has no taste or odour; iron and manganese causing staining and taste issues; and hardness from calcium and magnesium. Some Ontario regions also have elevated uranium and sodium in bedrock-sourced drilled wells. Our full panel addresses all of these parameters.

Question 3

Is well water testing required when buying a property?

Accepted Answer

Yes — for any property with a private well in Ontario or elsewhere in Ontario, most mortgage lenders and virtually all real estate lawyers require current well water test results satisfying Ontario Drinking Water Standards before financing and closing can proceed. A 'current' test is typically interpreted as less than 30–90 days old depending on the lender. The potability report must come from a MOH-accredited laboratory. ASADS provides MOH-compliant sample collection and accredited lab submission, with the written report formatted to satisfy lender and lawyer requirements for your Ontario property transaction.

Question 4

What if my water tests positive?

Accepted Answer

A positive or above-guideline test result does not necessarily mean the property is unmarketable — it means a treatment solution is required. For bacterial contamination (E. coli or coliform), UV disinfection systems and shock chlorination of the well are first-line responses. For nitrates, reverse osmosis or blended water systems are effective. For arsenic, reverse osmosis is the most reliable point-of-use treatment. For iron and hardness, water softeners and iron filters are standard. For active contamination events such as flooding or nearby spill, the well may need professional cleaning and disinfection. ASADS provides a written interpretation of your results and guidance on appropriate treatment options for your specific Ontario property.

Well Water Testing Ontario | E.coli, Bacteria & Arsenic