Water hardness in Renfrew
Renfrew, Ontario tap water is moderately hard, drawn from groundwater. Here is what it means at home, and the source.
What this means at home
Some kettle and showerhead scale over time, but most homes get by without a softener.
Treated-water hardness range reported for the Renfrew DWS; midpoint used.
You likely do not need a softener. Because the number moves around the city, test your own tap before you buy or set one.
New to this? Read hard water, explained, including whether it is safe to drink and how to test your tap.
The number, in real terms
At 64.2-144 mg/L mg/L (3.8 to 8.4 grains per gallon), a four-person Renfrew household puts only about 1,825 grains of hardness a day through its plumbing (industry sizing convention: about 300 US gallons a day). That is a light enough load that most homes skip the softener and just descale the kettle now and then.
Scale ceiling: every 1,000 litres heated can leave at most 104 grams of scale, because that is the total mineral carried at 64.2-144 mg/L mg/L. Real kettles and water heaters precipitate a fraction of that, but the ceiling scales with the number: Renfrew's moderately hard water leaves little behind.
How this is calculated: grains per gallon = mg/L divided by 17.1; daily grain load = gpg x 300 US gallons (the softener trade sizes in US gallons, four-person household); regeneration interval = 32,000 grains divided by the daily load; scale ceiling = mg/L carried per 1,000 L. The input figure is Ontario Clean Water Agency - Town of Renfrew 2024 Annual Drinking Water System Report's own published number, checked 2026-07-03. Full method on the methodology page.
Renfrew water hardness questions
How hard is the water in Renfrew?
Renfrew's tap water is moderately hard, about 64.2-144 mg/L mg/L as calcium carbonate (3.8 to 8.4 grains per gallon), drawn from groundwater. Figure from Ontario Clean Water Agency - Town of Renfrew 2024 Annual Drinking Water System Report, last checked 2026-07-03.
Do I need a water softener in Renfrew?
Probably not. Renfrew water is moderately hard, so most homes get by without one. A simple test kit settles it if you are unsure.
How does Renfrew compare with nearby towns?
Closest verified figures: London at 96-115 mg/L as CaCO3 mg/L, St. Clair at 102.5 mg/L as CaCO3 mg/L, Lambton Shores at approximately 98 to 106 mg/L as CaCO3 (West Lambton Shores via LAWSS about 98; East Lambton Shores via LHPWSS about 106) mg/L. Renfrew sits at 64.2-144 mg/L mg/L, all measured as calcium carbonate.
Source
Source: Ontario Clean Water Agency - Town of Renfrew 2024 Annual Drinking Water System Report, last checked 2026-07-03. Hardness varies by neighbourhood, season, and which well or plant serves your street, especially on groundwater systems. These are the municipal published figures as of the verified date, good for planning, not a substitute for a home test or your utility's current report.
Compare nearby verified figures: London (96-115 mg/L as CaCO3 mg/L), St. Clair (102.5 mg/L as CaCO3 mg/L), Lambton Shores (approximately 98 to 106 mg/L as CaCO3 (West Lambton Shores via LAWSS about 98; East Lambton Shores via LHPWSS about 106) mg/L). Or see every municipality.