Ion Exchange Water Softener Resin Capacity Calculator
Determine required Strong Acid Cation (SAC) resin volume, hardness throughput volume ($m^3$ or gal), and NaCl brine regeneration stoichiometry.
Water Hardness & Daily Demand
Resin Sizing & Brine Consumption
Recommended Tools & Equipment
Tested hardware and components for high reliability
Cation Exchange Softening & Regeneration Chemistry
Water softening utilizes cross-linked polystyrene divinylbenzene beads functionalized with sulfonic acid groups ($-\text{SO}_3^-\text{Na}^+$). As hard water flows through the bed, divalent calcium and magnesium ions displace monovalent sodium ions due to higher electrostatic charge affinity: $$2\,\overline{\text{R-SO}_3\text{Na}} + \text{Ca}^{2+} \rightleftharpoons \overline{(\text{R-SO}_3)_2\text{Ca}} + 2\,\text{Na}^+$$
Brine Regeneration Efficiency
Once the resin is exhausted with $\text{Ca}^{2+}$ and $\text{Mg}^{2+}$, a concentrated $10\%$ to $12\%$ sodium chloride brine solution is passed through the column. Mass action drives reverse equilibrium, stripping off hardness cations and restoring the resin to sodium form. Operating capacities typically range from $1.2$ to $1.6\text{ eq/L}$ depending on regenerant dosage.