Water Hardness & Softener Grain Sizing Calculator
Calculate required water softener grain capacity (32k, 48k, 64k grains), compensated hardness from iron, daily water usage, and monthly salt bags.
Calculated Results
Frequently Asked Questions
How is compensated water hardness calculated?
Clear dissolved iron puts heavy load on resin beads. Water treatment experts add 4 GPG of compensated hardness for every 1.0 PPM of dissolved iron. Formula: Compensated GPG = Hardness GPG + (Iron PPM × 4).
What size water softener do I need for a family of 4?
A standard family of 4 using 75 gallons per day with moderate-to-high hardness (12 to 18 GPG) typically requires a 32,000 to 48,000 grain system to regenerate once every 6 to 8 days.
What is the difference between GPG and PPM in water hardness?
1 Grain per Gallon (GPG) equals approximately 17.1 Parts per Million (PPM) or mg/L of calcium carbonate. Water above 10.5 GPG (180 PPM) is classified as 'Very Hard' by the Water Quality Association.
How often should a water softener regenerate?
Modern demand-initiated water softeners ideally regenerate once every 6 to 8 days. Regenerating too frequently wastes salt and water, while regenerating longer than 10 to 14 days causes iron fouling and channeling.