Water Test Results Centre
How to read a hardness result.
What hardness in mg/L or grains per gallon means for scale, soap and softeners — and what one number cannot tell you.
Unit
Usually mg/L as CaCO₃ or grains per gallon (gpg). 1 gpg ≈ 17.1 mg/L.
Canadian reference
Hardness is an aesthetic and equipment issue, not a Health Canada health MAC. Many Canadian municipal supplies are moderately to very hard; some coastal cities are very soft.
Possible sources
Dissolved calcium and magnesium from limestone and dolomite geology, or from the municipal blend serving your address.
What one result cannot conclude
- A city average is not your kitchen tap.
- Hardness does not prove iron, bacteria, lead or PFAS are absent.
- Scale on fixtures can also come from other deposits — confirm with a lab or hardness test kit used correctly.
Sensible follow-up testing
- If you are sizing a softener, test at the home and note peak flow (bathrooms, laundry).
- On wells, add iron, manganese, pH and tannins so resin is not fouled.
Source correction
You cannot ‘correct’ hardness at the source in a private well the way you might fix a contamination pathway. Treatment is the usual path once the number is confirmed.
Certification questions
Softeners are typically certified to NSF/ANSI 44 (cation exchange). That is not a contaminant-reduction claim for lead, PFAS or bacteria.
Treatment options
Ion-exchange softening addresses calcium and magnesium. Pair with carbon or RO only after you know the drinking-water goal. Very soft coastal supplies rarely need a softener.