How often should a private well be tested, and does my mortgage lender care about the results?

Ontario public health guidance generally recommends testing a private well's water at least a few times a year and after any event that could affect it, such as flooding, nearby construction, or a noticeable change in taste, colour, or smell. Testing typically covers bacteriological indicators, and periodically broader chemical parameters depending on the area and the well's history. Local public health units offer basic bacteriological testing, often at no cost, which makes regular testing an easy habit to keep up.

Lenders financing a rural property serviced by a private well commonly do care about water quality, and many will require a satisfactory water potability test, sometimes alongside a septic inspection, as a condition of approving the mortgage. This is separate from, and in addition to, any testing a buyer does for their own peace of mind. Because a single clean test only reflects conditions on the day it was taken, buyers should treat a pre-closing potability certificate as a snapshot, not a guarantee, and plan to keep testing regularly after taking ownership rather than assuming the well is permanently proven safe.