Canada Water Quality publishes two linked layers for each tracked municipality: (1) laboratory-style parameters used for grading and comparison, and (2) a supply profile that describes source type, source waters, treatment plants, and distribution notes. Shared OpenStats ranking rules live on the hub methodology page; this page covers water-specific rules.
Coverage
The atlas tracks 172 municipalities across provinces and territories. Of those, 29 carry a direct municipal data tier for hardness and related parameters, and 143 carry a regional estimate until a direct report is ingested. Supply profiles cover 172 cities (121 surface water, 30 groundwater, 21 mixed surface and groundwater). 172 profiles name source waters; 172 cite utility or municipal publications. Research confidence on supply notes: 130 high, 42 medium, 0 low.
Parameter ingest
Hardness (mg/L as CaCO₃), pH, lead, fluoride, free chlorine, and turbidity where published are taken from municipal or utility water quality reports and related open releases. Pipelines record the source and reading date. There is no single Statistics Canada table of municipal tap hardness for all Canadian cities; coverage expands as named reports are verified. Figures are not invented to fill gaps.
Health Canada's Guidelines for Canadian Drinking Water Quality, maintained with the Federal-Provincial-Territorial Committee on Drinking Water, frame hardness as an operational / aesthetic parameter without a maximum acceptable concentration. Summary guidance notes that water above about 200 mg/L hardness is generally considered poor for domestic use and levels above about 500 mg/L are typically unacceptable for most domestic purposes, while calcium and magnesium at levels found in drinking water are not treated as a health MAC concern. Provinces adopt guideline values into their own drinking-water programs; utilities sample and publish under those rules. See the hub drinking water hardness guide for class bands, units, and softener context.
Data tiers
- Direct. Parameters come from a report for that municipality or its named utility. These pages may be indexed.
- Regional. The best available broader estimate is shown and labeled. Regional city pages stay noindex for search until a direct municipal reading replaces the estimate.
Supply profiles can still document source type and plants for regional-tier cities when utilities publish that information separately from the hardness series.
Grades
Letter grades summarize guideline compliance for pH, lead, fluoride, and free chlorine using Health Canada thresholds encoded in the atlas (including lead ≤ 5 μg/L). Hardness has no health MAC; it is classified (soft / moderate / hard / very hard) for everyday interpretation and compared to provincial sample averages on the gauge. Grades support browsing and comparison. They are not a substitute for a licensed lab test of your tap or for an active advisory.
Supply profiles
Every tracked city carries a supply and treatment profile researched from utility and municipal publications: annual reports, source-water protection plans, treatment process pages, capital plans, and related open documents. The city-page section states source type (surface, groundwater, or mixed), named source waters when published, treatment plant names and plant notes, distribution notes, a short local note when the source materials support one, and outbound citation links.
Coverage today: 172 profiles (121 surface water, 30 groundwater, 21 mixed surface and groundwater). 172 name source waters; 172 carry cited source URLs. Research confidence: 130 high, 42 medium, 0 low.
Profiles do not invent plant lab numbers or fill missing hardness, lead, or other chemistry fields. Laboratory-style parameters stay on the graded parameter record and are ingested only from named municipal or utility reports. When a utility describes a plant process but does not publish a hardness series for that city, the supply section may still list the plant while the parameter tier remains regional or pending. Confidence (high / medium / low) reflects how directly the cited materials support the prose summary, not a statistical margin of error.
Corrections: email [email protected] with the city URL, the field, and a link to the official document. Verified updates land in the next scheduled refresh. Named publishers also appear on data sources.
Advisories
Boil-water and related advisories are listed on /advisories/ and surfaced on city pages when active. An advisory is a safety notice from the responsible authority; it overrides routine hardness or grade interpretation for immediate decisions.
Why cities differ
Source geology and treatment dominate hardness differences. Groundwater and limestone-influenced rivers often finish harder than large lake or protected reservoir supplies. Blending, seasonal source switches, lime softening, and membranes can move finished hardness relative to raw water. Supply profiles on city pages document source type and plants so readers can see those drivers beside the parameter table.
Limitations
Plant averages and community samples are not the same as a measurement at a specific kitchen tap. Lead can vary with premise plumbing. Hardness classes are conventional, not regulatory MACs. Private wells require separate provincial lab programs. For health decisions, rely on the issuing municipality or utility, a licensed professional, or Health Canada guidance. Named datasets: data sources. Hub overview: openstats.ca/methodology. Guidelines: Health Canada summary table.