How our summaries are made

What you see on a report page

• A short status — one of three lines (below), driven by recent public testing and enforcement records.
• Day-to-day notes — hardness, sodium, and similar, when a separate lab program has samples for that supply. Full cards live on the system report. City pages may show only elevated notes on each municipal system card — never a city-wide average.
• Collapsed detail — counts, older context, and system numbers if you open them.

There is no single safe/unsafe score. The data cannot support one for your exact tap.

The three status lines

• Worth a closer look — recent public records include a result above an Ontario standard, a water-quality report, a provincial order, or a name-matched conviction. The page always says which.
• Nothing major stood out — those items did not show up in the recent file we use.
• Not enough recent data — too few recent records to summarize with confidence.

What this is not

• Not a test of your kitchen tap or building pipes.
• Not real-time alerts — open data lags behind current notices.
• Not medical or legal advice.

More on that limit: public records vs your home tap.

Where the numbers come from

Status and “closer look” items come from Ontario’s drinking-water quality and enforcement open data (tests, incidents, orders, inspections, and related notes) for recent years — currently through 2024-25.

Day-to-day mineral cards come from a separate surveillance program, only for systems that took part. Missing cards mean “no samples in that program here,” not a warning. We do not merge plant readings into one city hardness or sodium figure. Full list: data sources.

Technical notes (optional)

• Recent public records — the recent fiscal years we process for status (currently four years of enforcement/quality files).
• Over-limit test — a flag already in the source data for an Ontario drinking-water standard. We show the flag and the substance name; we do not invent our own limits.
• Incident record — a reportable event in the public file (also called an adverse water quality incident in source data). A count is not a count of taps affected.
• Matched conviction — matched by exact system name. No match means none in our data, not proof that none ever existed.
• School and child-care water records stay separate from town supply records.
• Hardness labels use three resident bands from long-term plant samples (soft ≤60, hard 60–180, very hard >180 mg/L as CaCO₃). Other day-to-day compare lines follow Ontario standards and objectives (O. Reg. 169/03 and provincial aesthetic / operational guidance; sodium diet notice at 20 mg/L). See Ontario drinking-water standards.
• When a field is missing, pages say so instead of guessing. The province republishes datasets over time; we rebuild when new data lands. Official records always win if wording differs.