Water hardness in Guelph
332 mg/L very hard
Tap water in Guelph is very hard: 332 mg/L (19.4 gpg · 18.6 °dH · 33.2 °fH).
Source: Ontario Ministry of the Environment, Conservation and Parks, Drinking Water Surveillance Program, Open Government Licence – Ontario (2019) · data checked 2026-10-21
This figure is over 3 years old; hardness may have changed.
Guelph relies mainly on groundwater drawn from the dolostone aquifers beneath the city, which is why the water is hard. The Ontario surveillance programme reported 332 mg/L as CaCO3 for 2019, with no range published. Many local households use softeners, and scale builds up quickly on heaters and fixtures.
Health Canada: hardness above 200 mg/L is considered poor but tolerable; above 500 mg/L unacceptable.
Water data
| Total hardness | 332 mg/L |
|---|---|
| Utility | Guelph Drinking Water System |
How Guelph compares
- Tap water in Guelph is 228 % harder than the median of the 254 cities we track in Canada (101 mg/L).
- By hardness it ranks 14 of 254 in Canada (1 = hardest); 95 % of these cities have softer water.
- In Ontario it is number 13 of 120 cities; the regional median is 124 mg/L.
- Nearest city with clearly softer water: Milton, 30 km away (222 mg/L).
- Nearest city with clearly harder water: Fergus, 20 km away (519 mg/L).
Ranking of the hardest and softest water in Canada →
What it means at home
- Severe scale: heater elements and washing-machine heaters fail early.
- Detergent use is very high; taps and screens coat within days.
- Dishwasher at maximum salt setting.
- An ion-exchange softener is practically essential; RO for drinking water.
How much salt will you use for softening?
Yes. At this hardness a softener pays for itself through appliance life and detergent.
Descale a coffee machine or kettle about every 1 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Guelph
| Brand | Setting for this water |
|---|---|
| Bosch | H05 |
| Miele | 19 °dH |
| AEG / Electrolux | 4 |
| Beko | 5th |
| Hoover | S3 |
| LG | H3 |
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 Guelph water hard or soft?
It is very hard: 332 mg/L as CaCO₃ (19.4 gpg, 18.6 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Guelph 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 Guelph water?
19.4 gpg, equal to 18.6 °dH, 33.2 °fH or 332 mg/L calcium carbonate.
What dishwasher salt setting should I use in Guelph?
For 332 mg/L (18.6 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Guelph?
Yes, unless you are only passing through: scale damages appliances within a few years.
Source
Source: Ontario Ministry of the Environment, Conservation and Parks, Drinking Water Surveillance Program, Open Government Licence – Ontario (2019). 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