Peterborough Water Hardness & Quality Report (2026)

The City of Peterborough, Ontario, Canada, and surrounding areas in Peterborough County receive their drinking water from the Peterborough Utilities Commission (PUC). This supply originates solely from the Otonabee River, which eventually flows into Lake Ontario via the Trent River system. The PUC Water Treatment Plant, situated near the river intake on the city's west side, is responsible for treating this raw water. The utility adheres to regulations set by Ontario's Ministry of the Environment, Conservation and Parks, performing over 20,000 tests each year to ensure water quality for the roughly 130,000 residents served.

The Otonabee River watershed, covering approximately 1,700 square kilometers in the Kawartha Lakes region, is underlain by Paleozoic bedrock dating back to the Ordovician period. This includes formations of limestone and dolostone. As these rocks weather, they release minerals, particularly calcium and magnesium, into the surface runoff. This geological influence gives the water its characteristic moderately mineralized quality. While groundwater from similar limestone aquifers in central Ontario would typically be harder, the river water is somewhat softer due to dilution and the presence of organic matter from wetlands and forests within the watershed.

Homeowners may notice moderate scale buildup on fixtures and in appliances, which can reduce the efficiency of appliances like water heaters and dishwashers by up to 30%. You'll also find that soap doesn't lather as readily, often requiring more detergent for cleaning. Spotting on glassware after washing is another common sign. To manage this, periodic descaling of fixtures with vinegar is advised. For those looking to extend the life of their plumbing and improve cleaning effectiveness, installing a water softener is a good recommendation, especially since the effects of this moderate hardness are quite noticeable.