Water hardness in Ottawa
36 mg/L soft
Tap water in Ottawa is soft: 36 mg/L (2.1 gpg · 2 °dH · 3.6 °fH).
Source: Ontario Ministry of the Environment, Conservation and Parks, Drinking Water Surveillance Program, Open Government Licence – Ontario (2016) · data checked 2026-10-21
Range across supply zones: 31–40 mg/L.
This figure is over 3 years old; hardness may have changed.
Ottawa's drinking water comes from the Ottawa River, treated at the Britannia and Lemieux Island plants. The figure of 35.9 mg/L as CaCO3 (range 31.2 to 39.6) is from Ontario's Drinking Water Surveillance Program for 2016, so it is not current-year data. The water is soft, and scale in kettles is minor.
Health Canada: hardness above 200 mg/L is considered poor but tolerable; above 500 mg/L unacceptable.
Water data
| Total hardness | 36 mg/L |
|---|---|
| Utility | Central Drinking Water System - Britannia; Central Drinking Water System - Lemieux Island |
How Ottawa compares
- Tap water in Ottawa is 65 % softer than the median of the 254 cities we track in Canada (101 mg/L).
- By hardness it ranks 184 of 254 in Canada (1 = hardest); 28 % of these cities have softer water.
- In Ontario it is number 114 of 120 cities; the regional median is 124 mg/L.
- Nearest city with clearly softer water: Pembroke, 119 km away (12 mg/L).
- Nearest city with clearly harder water: Clarence-Rockland, 35 km away (46 mg/L).
Ranking of the hardest and softest water in Canada →
What it means at home
- Little or no limescale in kettles, water heaters or washing machines.
- Soap lathers easily; water does not dry skin or hair.
- Dishwasher: salt setting at minimum or off.
- No softener needed; a jug filter only changes taste.
How much salt will you use for softening?
No. Water this soft does not need softening.
Descale a coffee machine or kettle about every 6 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Ottawa
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 2 °dH |
| AEG / Electrolux | 1 |
| Beko | 1st |
| Hoover | S0 |
| LG | H0 |
From each brand's manual for the model family named in the source; your model may differ, so check its manual. All brands and how to change the setting →
FAQ
Is Ottawa water hard or soft?
It is soft: 36 mg/L as CaCO₃ (2.1 gpg, 2 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Ottawa safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. Health Canada: hardness above 200 mg/L is considered poor but tolerable; above 500 mg/L unacceptable.
How many grains per gallon is Ottawa water?
2.1 gpg, equal to 2 °dH, 3.6 °fH or 36 mg/L calcium carbonate.
What dishwasher salt setting should I use in Ottawa?
For 36 mg/L (2 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Ottawa?
No. With soft water a softener adds nothing.
Source
Source: Ontario Ministry of the Environment, Conservation and Parks, Drinking Water Surveillance Program, Open Government Licence – Ontario (2016). Method: figure published by the water supplier. Ontario Ministry of the Environment, Conservation and Parks, Drinking Water Surveillance Program, Open Government Licence – Ontario · Outdated figure? Tell us