Water softener sizing worksheet
A working-capacity estimate for a salt-regenerated household softener, plus five-year salt and regeneration-water cost. Supply your own measurements and prices.
Water and capacity
Enter working grains per regeneration at the intended salt dose, not just a marketing/maximum grain label. If you only know the label, ask the manufacturer for working capacity. The 7-day value is a scenario you can edit, not a universal rule.
Cost assumptions
Salt and regeneration-water amounts are editable examples, not model-specific claims. Use local combined water/sewer rate if billed on the extra water.
Worksheet
Sizing by grains does not check peak household flow, pressure drop, iron or manganese, brine settings, reserve capacity, local discharge rules or drinking-water suitability. A softener is not a contaminant-removal guarantee. Verify the exact model's working capacity and salt/water use with its manual.
Basis: Penn State Extension, Water Softening, updated September 8, 2025 (accessed September 27, 2026): daily gallons × hardness in grains/gal gives daily grain demand; working grain capacity ÷ daily demand gives days between regenerations. Its worked example is 300 gallons/day × 10 grains/gal = 3,000 grains/day; 20,000 grains gives about 6–7 days. The range below shows 5–10 days for comparison only, not Penn State's recommended interval. Five years is modeled as 365 × 5 days, with steady demand and regeneration at the earlier of the entered interval or estimated capacity exhaustion (for zero hardness, the entered timer interval), no price increases, no maintenance, equipment, installation or tax. Dollar prices are never supplied by this site.