Ontario

Toronto water hardness

The City of Toronto's 2025 drinking water analysis averaged 119 mg/L of hardness across 119 samples, ranging from 115 to 122 mg/L. That is moderately hard, just under the 120 mg/L line, and above Ontario's operational guideline of 80 to 100 mg/L, which the City prints next to its results.

Data last reviewed October 17, 2026.

City of Toronto

119 mg/L as CaCO₃ Moderately hard
  • Average
  • Range: 115 to 122 mg/L
  • 119 samples

In other units

US grains per gallon
7.0
Imperial grains per gallon
8.4
German degrees (°dH)
6.7
Millimoles per litre
1.19

Source: City of Toronto, Drinking water analysis summary, 2025 (PDF). Data for: 2025, annual analysis summary. Checked October 13, 2026.

What this means for your appliances

Moderately hard

Some scale builds up over time, mostly where water gets heated: kettles, coffee makers and washers. A monthly clean keeps it in check.

Recommended for your water

Dishwasher Cleaner

5.0(15)

Dissolves grease, detergent residue and limescale buildup, and removes odour-causing buildup.

Clears grease, limescale and odour buildup

$23.95

Washing Machine Cleaner

4.9(14)

Breaks down residue and odour-causing buildup inside your washer.

Removes odour and buildup from the drum and hoses

$24.95

Coffee Maker Cleaner

4.8(14)

Removes limescale, mineral buildup and coffee oils inside your coffee maker.

Descales for better-tasting coffee

$24.95

Guides for hard water

What counts as hard water?

We use the U.S. Geological Survey scale, in mg/L as CaCO₃.

  • Soft 0 to 60 mg/L
  • Moderately hard 61 to 120 mg/L
  • Hard 121 to 180 mg/L
  • Very hard Over 180 mg/L

How to read the units

Utilities usually report hardness in mg/L as calcium carbonate (CaCO₃), which is the same as ppm. Dishwasher and softener manuals often use grains per gallon or German degrees instead. Here is how they convert:

  • 1 US grain per gallon = 17.1 mg/L
  • 1 imperial grain per gallon = 14.25 mg/L
  • 1 °dH = 17.85 mg/L
  • 1 mmol/L = 100.09 mg/L

Questions and answers

Is Toronto water hard?

Moderately hard. The City of Toronto's 2025 results averaged 119 mg/L, just under the 120 mg/L line for hard water and above Ontario's operational guideline of 80 to 100 mg/L.

Does this include Mississauga or Brampton?

No. Mississauga and Brampton get their water from Peel Region, which publishes its own results. This page covers the City of Toronto only.

What is Toronto's water hardness in grains per gallon?

City of Toronto: 7.0 grains per US gallon, or 8.4 grains per imperial gallon.

Where do these numbers come from?

City of Toronto, Drinking water analysis summary, 2025 (PDF). Data for 2025, annual analysis summary. We update this page when a new report comes out.

Sources

Check another city