Ontario drinking-water standards
This site is about Ontario public drinking-water records. Compare lines on hardness, sodium, chloride, nitrate, fluoride, and pH follow Ontario’s legal and technical framework — not a federal ranking.
SDWA 2002
provincial law
O. Reg. 169/03
quality standards
Open data
what we summarize
Official Ontario sources
Start at Ontario’s public drinking-water hub, then the Act and the quality-standards regulation that operators and inspectors use.
- ontario.ca — Drinking water — systems, testing, annual reports, and program overview.
- Safe Drinking Water Act, 2002 — the provincial statute for safe drinking water.
- O. Reg. 169/03 — Ontario Drinking Water Quality Standards — prescribed microbiological and chemical standards (including nitrate and fluoride limits used on this site).
Open Ontario drinking water hub →
How our six day-to-day notes map
| Parameter | Ontario framework | On this site |
|---|---|---|
| Hardness | No health MAC in O. Reg. 169/03. Operational materials may discuss treatment bands (often ~80–100 mg/L as CaCO3) — not a “unsafe tap” score. | Soft ≤60; hard 60–180; very hard >180. Comfort and appliances only. |
| Sodium | Not a primary health MAC in the same way as nitrate. Ontario practice: report so people on low-sodium diets can plan; aesthetic objective ~200 mg/L (taste). | Diet notice at 20 mg/L; taste line at 200 mg/L. |
| Chloride | Aesthetic objective ≤250 mg/L in Ontario ODWS materials. | Elevated note at ≥250 (taste / plumbing interest). |
| Nitrate | O. Reg. 169/03 standard: 10.0 mg/L as nitrogen. | Elevated note at ≥10 mg/L as N. |
| Fluoride | O. Reg. 169/03 standard: 1.5 mg/L. | Elevated at ≥1.5. Dental target ~0.5–0.8 where communities add fluoride (not the legal maximum). |
| pH | Ontario operational guidance commonly 6.5–8.5 for treated water. | Usual range 6.5–8.5; outside is treatment/pipe context. |
What these lines are not
- Not a “safe / unsafe” score for your kitchen glass. Plant averages and household plumbing differ.
- Day-to-day DWSP averages are not the same as a formal exceedance under O. Reg. 169/03 — compliance flags and incident records live in a different open dataset on this site.
- Not medical advice. Diet or infant questions: talk to a clinician and your municipality.
Short household meanings:
what the day-to-day numbers mean.
Raw open-data catalogue links:
data sources.