Two numbers do most of the sorting in the library.
Mineral class, by TDS
- Very low: under 50 mg/L
- Low: 50 to 500 mg/L
- Medium: 500 to 1,500 mg/L
- High: over 1,500 mg/L
Of the 26 verified waters, 13 are low, 6 are medium, 4 are high, 3 are very low.
Hardness
Hardness is calculated from calcium and magnesium and expressed as mg/L of calcium carbonate: 2.497 × calcium + 4.118 × magnesium.
The calcium to magnesium ratio
Around 2 reads as balanced. Above 10, calcium dominates the taste.