Ion exchange · capacity and flow

Industrial water-softener sizing

Solve both sides of the problem: resin capacity for the hardness load and resin volume for the peak hydraulic flow. The larger result controls.

Controlling resin volume

Capacity controls

max(load, flow)

Selected resin per online duty bed160L5.7 ft³ · 320 L total installed

Required cycle capacity8.65 kg CaCO₃7.35 kg actual load; balance held in reserve

Resin required by flow100 L18.8 BV/h after selection

Salt per regeneration / bed19.2 kgat entered manufacturer dosage

Design note:

Two limits, one answer

Capacity gets you through the run; flow gets you through the peak.

The answer is per online duty bed. In alternating duplex service, each vessel is sized for the full peak and the second is ready while the first regenerates.

Actual load = hardness removed × m³/day × daysRequired capacity = actual load ÷ (1 − reserve)Capacity resin = required capacity ÷ manufacturer working capacityFlow resin = peak flow × 1000 ÷ max BV/h

What this does not decide

The resin datasheet and water analysis still govern.

Account for iron, manganese, TDS, temperature and fouling.
Verify valve service/backwash/brine flows and injector.
Select simplex, alternating duplex or parallel duty for continuity.
Use the selected resin’s actual salt-efficiency curve.

Check the assumptions

Method and primary references

The equations are shown so the result can be checked. Product data and site conditions still govern final selection.

Purolite C100 Sodium CycleManufacturer operating-capacity and regeneration guidance.
DuPont Water Conditioning ManualIon-exchange design, flow and capacity background.

From answer to equipment

Bring the duty point, not just a product name.

Watermart can check the calculation against the actual water analysis, pressure, valve, pump and installation constraints.

Discuss this calculation →

Educational preliminary calculation—not a stamped design, quotation, or treatment-performance guarantee.