RO System Calculators
RO System Calculators
Field-standard reverse osmosis design formulas — size a system, check recovery and scaling risk, and estimate operating cost before you call for a quote.
Design Inputs
Design GPD = peak demand × safety factor, then converted to a per-minute production rate over your planned run window (typically 10–12 hrs/day rather than continuous, to allow CIP and downtime). Safety-factor convention per industry sizing guides — treat as a starting point, not a substitute for engineering review.
System Output
Stream Data
Recovery = permeate ÷ feed flow. Rejection = 1 − (permeate TDS ÷ feed TDS). Typical brackish RO runs 70–85% recovery; seawater RO 35–50%; healthy membranes reject 97–99% of salts.
Performance
Concentrate Stream Chemistry
Langelier Saturation Index (LSI) on the concentrate stream — always the highest-risk point in the system since recovery concentrates hardness and alkalinity. LSI > 0 signals CaCO₃ scaling risk and typically calls for antiscalant dosing or a lower recovery target. Run concentrate-side numbers, not raw feed water.
Scaling Index
Cost Inputs
Cost = energy (kWh × rate) + membrane replacement amortized monthly + chemicals/consumables. Typical commercial RO cost mix: power ~35–45%, membranes ~5–10%, chemicals ~5–15%, balance labor/maintenance not modeled here.
Estimated Cost
Flow — GPD → LPD
Flow — GPM → m³/day
Volume — US Gallons → Liters
Pressure — PSI → Bar
Formulas follow standard industry sizing and water-chemistry conventions and are provided for preliminary estimating only — final system design should be confirmed by an AMPAC applications engineer.
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