We'll say your water hardness is 15 grains per gallon and you have a family of 3. You have a 24,000 grain water softener. Your family of three will use 225 gallons of water per day (3 X 75). Since the water has 15 grains of hardness, you'll need to treat 3375 grains of hardness per day (225 X 15).read more >>