Cooling Tower Water Balance & LSI Calculator
A vendor-neutral evaporation, drift, blowdown, and makeup water balance calculator for industrial cooling towers, paired with a Langelier Saturation Index (LSI) and Ryznar Stability Index (RSI) model that dynamically flags scaling and corrosion risk in the circulating water.
Design Reference Ranges
Need a custom review?
For non-standard makeup water chemistry, closed-loop systems, or a full scale/corrosion control program, our engineers can provide a detailed process audit.
Request ConsultationExport Capabilities
- Professional PDF engineering reports
- Combined water balance + LSI/RSI record
- Metric / Imperial unit conversion
- Makeup-water-to-circulating-water estimation
Cooling Tower Water Balance & LSI Calculator
Evaporation, drift, blowdown and makeup water balance from mass conservation, plus Langelier Saturation Index scaling/corrosion risk screening for the circulating water.
Cooling range (ΔT): —
Typical operating range: 3–6.
Default 0.00153 (metric, m³/h & °C basis) — see methodology note below. Typical range 0.00115–0.00195 for climate variation.
If you only have makeup water lab data on hand, enter it here and estimate the concentrated circulating-water values (Ca, Alkalinity, TDS all scale × CoC at steady state). pH does not scale this way — enter your own circulating water pH reading above.
Achieved CoC: —
Heat rejected (informational): —
Export includes the current water balance and water chemistry configuration and results.
Evaporation coefficient: the commonly cited "0.0008/0.00085 × flow × range" rule of thumb is an imperial constant (gpm, °F) — used directly against a Celsius ΔT without the required ×1.8 unit conversion it understates evaporation by roughly 1.8×. This tool defaults to the converted metric constant, 0.00153, cross-checked against the independent "~1% evaporation per 5.6°C range" industry rule of thumb.
Engineering Methodology
Evaporation, drift, and blowdown follow a standard mass-conservation water balance (CTI/ASHRAE convention): evaporation loss is proportional to circulating flow x cooling range, drift loss follows the selected drift eliminator performance class, and forced blowdown is solved directly from a steady-state Cycles of Concentration mass balance.
Scaling/corrosion tendency uses the Langelier Saturation Index (Langelier, 1936) computed from water temperature, pH, calcium hardness, total alkalinity, and TDS, with the Ryznar Stability Index included as a secondary cross-check — both are empirical screening indices, not a substitute for a full water treatment chemical program.
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