Should I test my rural well for arsenic or uranium in parts of Ontario known for naturally occurring contamination?

Yes. Unlike bacterial contamination, which can come from surface sources like septic systems or flooding, substances like arsenic and uranium can occur naturally in bedrock and groundwater in certain parts of Ontario, meaning a well can have elevated levels even with no nearby pollution source and no visible change in water taste, colour, or smell. Because these substances aren't part of routine basic bacteriological testing offered by local public health units, a buyer relying only on that standard test could miss them entirely.

If you're buying in, or your well draws from, an area with a known geological history of these contaminants, it's worth arranging specific chemical testing for arsenic, uranium, and other relevant parameters as part of your pre-purchase due diligence, separate from the bacteriological test many lenders require. Local health units and provincial resources can generally indicate whether an area has known naturally occurring water quality issues. Because these contaminants can pose long-term health risks and typically require dedicated treatment systems to address if found, identifying the issue before closing gives far more room to negotiate remediation costs or reconsider the purchase than discovering it afterward.