With municipal water. the usual recommended regeneration frequency will be between 7-days and 30-days.
For 100 gallons/day X 23 gpg = 2300 grains/day consumption.
A 1 ft3 softener will provide 24K grains capacity when programmed for 3,000 grain/lb efficiency. 24,000 / 2,300 = 10.4 days anticipated between regeneration cycles. As a Reserve allowance will need to be subtracted, the realistically anticipated regeneration frequency will be 9-10 days.
A 1 ft3 softener will provide 21K grains capacity when programmed for 3,500 grain/lb efficiency. 21,000 / 2,300 = 9.13 days anticipated between regeneration cycles. As a Reserve allowance will need to be subtracted, the realistically anticipated regeneration frequency will be 8-9 days.
A 1 ft3 softener will provide 17K grains capacity when programmed for 4,250 grain/lb efficiency. 17,000 / 2,300 = 7.39 days anticipated between regeneration cycles. As a Reserve allowance will need to be subtracted, the realistically anticipated regeneration frequency will be 6-7 days.
Comparison calculations for a 1.5 ft3 softener:
A 1.5 ft3 softener will provide 36K grains capacity when programmed for 3,000 grain/lb efficiency. 36,000 / 2,300 = 15.6 days anticipated between regeneration cycles. As a Reserve allowance will need to be subtracted, the realistically anticipated regeneration frequency will be 14-15 days.
A 1.5 ft3 softener will provide 31.5K grains capacity when programmed for 3,500 grain/lb efficiency. 31,500 / 2,300 = 13.7 days anticipated between regeneration cycles. As a Reserve allowance will need to be subtracted, the realistically anticipated regeneration frequency will be 12-13 days.
A 1.5 ft3 softener will provide 25.5K grains capacity when programmed for 4,250 grain/lb efficiency. 25,500 / 2,300 = 11.0 days anticipated between regeneration cycles. As a Reserve allowance will need to be subtracted, the realistically anticipated regeneration frequency will be 10-11 days.