Water hardness in Peterborough
95 mg/L moderately hard
Tap water in Peterborough is moderately hard: 95 mg/L (5.6 gpg · 5.3 °dH · 9.5 °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: 94–97 mg/L.
This figure is over 3 years old; hardness may have changed.
Peterborough draws from the Otonabee River and treats it at a single municipal plant. The surveillance programme reported 95.4 mg/L as CaCO3 for 2016 (93.6 to 97.2). The water is moderately soft, and scale builds up slowly.
Health Canada: hardness above 200 mg/L is considered poor but tolerable; above 500 mg/L unacceptable.
Water data
| Total hardness | 95 mg/L |
|---|---|
| Utility | Peterborough Drinking Water System |
How Peterborough compares
- Tap water in Peterborough is 6 % softer than the median of the 254 cities we track in Canada (101 mg/L).
- By hardness it ranks 135 of 254 in Canada (1 = hardest); 47 % of these cities have softer water.
- In Ontario it is number 94 of 120 cities; the regional median is 124 mg/L.
- Nearest city with clearly softer water: Gravenhurst, 108 km away (42 mg/L).
- Nearest city with clearly harder water: Port Hope, 32 km away (123 mg/L).
Ranking of the hardest and softest water in Canada →
What it means at home
- Visible kettle scale every few weeks; vinegar or citric acid is enough.
- Water heater and washing machine: some long-term scale; a scale inhibitor slows it.
- Dishwasher: medium salt setting.
- Softener optional; pays off mainly with a gas boiler or tankless heater.
How much salt will you use for softening?
Optional. A scale inhibitor or a small softener protects the heater; soap savings are modest.
Descale a coffee machine or kettle about every 3 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Peterborough
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 5 °dH |
| AEG / Electrolux | 2 |
| Beko | 2nd |
| Hoover | S1 |
| LG | H1 |
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 Peterborough water hard or soft?
It is moderately hard: 95 mg/L as CaCO₃ (5.6 gpg, 5.3 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Peterborough 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 Peterborough water?
5.6 gpg, equal to 5.3 °dH, 9.5 °fH or 95 mg/L calcium carbonate.
What dishwasher salt setting should I use in Peterborough?
For 95 mg/L (5.3 °dH) check your manufacturer's table: level 2–3.
Do I need a water softener in Peterborough?
Not essential; a scale inhibitor protects the heater cheaply.
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