Water Softener Size Calculator

Multiply: (Number of People) × (Daily Water Usage, ~75 gallons) × (Water Hardness in GPG). This gives your daily grain requirement. Multiply by 7 for weekly needs, then choose a softener with slightly higher capacity. Example: 4 people × 75 gal × 10 GPG = 3,000 grains/day × 7 = 21,000 grains/week → Choose a 24,000 or 32,000 grain softener.

A 4-bedroom house typically has 3-5 occupants. With average water hardness (10 GPG), you'd need: 4 people × 75 gal × 10 GPG = 3,000 grains/day = 21,000 grains/week. A 32,000-grain softener is ideal, providing about 10 days between regenerations. For very hard water (15+ GPG), consider a 40,000-48,000 grain unit.

A 48,000-grain softener is suitable for larger households (5-6 people) or homes with very hard water (15+ GPG). For a family of 4 with moderately hard water (10 GPG), it would regenerate only every 2+ weeks, which is actually too infrequent—resin can develop issues if not regenerated regularly. A 32,000-grain unit is often more efficient for average families.

Yes, size matters significantly. An undersized softener regenerates too frequently, wasting salt and water while wearing out faster. An oversized softener may not regenerate often enough (ideally every 7-10 days), leading to resin fouling and channeling. The right size balances capacity with efficient regeneration frequency.

A family of 2 typically needs: 2 people × 75 gal × water hardness (GPG). With moderate hardness (10 GPG): 1,500 grains/day = 10,500 grains/week. A 16,000-24,000 grain softener is ideal. With very hard water (15+ GPG): 2,250 grains/day = 15,750 grains/week, suggesting a 24,000-grain unit.

Optimal regeneration is every 7-10 days. More frequent regeneration (every 2-3 days) indicates an undersized unit and wastes salt/water. Less frequent (every 2+ weeks) can cause resin problems. Modern demand-initiated systems regenerate based on actual usage, which is most efficient. Size your softener so it naturally regenerates weekly under normal use.