Water treatment calculations

Practical calculators for RO, softeners, flow, and tank checks

Quick reference tools for engineers, contractors, site teams, and water treatment companies. Results are guide calculations and should be checked against equipment manuals, site conditions, and project specifications.

RO Recovery

Enter any two flows to calculate the third, recovery percentage, and permeate/reject ratio.

Feed flow Permeate flow Reject flow Recovery: - | Reject flow: - | Permeate/reject ratio: -

Recovery % = permeate / feed x 100. Feed = permeate + reject.

RO Salt Rejection

Feed conductivity Permeate conductivity Salt rejection: -

Salt rejection % = (1 - permeate conductivity / feed conductivity) x 100.

Softener Capacity

Resin volume, litres Capacity per litre resin, m3 at 1 ppm as CaCO3 Raw water hardness, ppm as CaCO3 Estimated throughput before regeneration: -

Throughput m3 = resin litres x capacity per litre / hardness. The default capacity factor is a rough estimate only.

Hardness Conversion

Hardness, ppm as CaCO3 Clark: - | dH: - | fH: -

Flow Conversion

Flow, m3/hr L/min: - | L/sec: -

Tank Volume

Length Width Water depth / fill height Volume: -

Volume m3 = length x width x water depth. Litres = m3 x 1000.