Water hardness in Oakville
127 mg/L hard
Tap water in Oakville is hard: 127 mg/L (7.4 gpg · 7.1 °dH · 12.7 °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: 122–132 mg/L.
This figure is over 3 years old; hardness may have changed.
Oakville is supplied from Lake Ontario through the South Halton system, with an Oakville treatment plant. The Ontario surveillance programme reported 127 mg/L as CaCO3 for 2016, ranging from 122 to 132. That reading is hard by the common 120 mg/L threshold, so expect scale on heating elements.
Health Canada: hardness above 200 mg/L is considered poor but tolerable; above 500 mg/L unacceptable.
Water data
| Total hardness | 127 mg/L |
|---|---|
| Utility | South Halton Drinking Water System - Oakville |
How Oakville compares
- Tap water in Oakville is 25 % harder than the median of the 254 cities we track in Canada (101 mg/L).
- By hardness it ranks 77 of 254 in Canada (1 = hardest); 70 % of these cities have softer water.
- In Ontario it is number 46 of 120 cities; the regional median is 124 mg/L.
- Nearest city with clearly softer water: Collingwood, 123 km away (86 mg/L).
- Nearest city with clearly harder water: Milton, 18 km away (222 mg/L).
Ranking of the hardest and softest water in Canada →
What it means at home
- Fast scale on taps, shower screens and kettle; white spots on glassware.
- Water heater: efficiency loss and element failures within years if unprotected.
- Dry skin and dull hair after showering are common.
- Softener recommended; jug or reverse osmosis for drinking.
How much salt will you use for softening?
Recommended, especially with a heater or boiler: scale cuts efficiency and shortens its life.
Descale a coffee machine or kettle about every 2 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Oakville
| Brand | Setting for this water |
|---|---|
| Bosch | H01 |
| Miele | 7 °dH |
| AEG / Electrolux | 2 |
| Beko | 2nd |
| Hoover | S1 |
| LG | H2 |
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 Oakville water hard or soft?
It is hard: 127 mg/L as CaCO₃ (7.4 gpg, 7.1 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Oakville 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 Oakville water?
7.4 gpg, equal to 7.1 °dH, 12.7 °fH or 127 mg/L calcium carbonate.
What dishwasher salt setting should I use in Oakville?
For 127 mg/L (7.1 °dH) check your manufacturer's table: level 4–5.
Do I need a water softener in Oakville?
Recommended if you have a water heater, boiler or tankless unit: it saves repairs and detergent.
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