Formula used
The calculator reports an approximate LSI and a practical risk score for irrigation scaling. LSI estimates calcium carbonate tendency using pH, temperature, alkalinity, calcium hardness, and TDS.
Approximate LSI: LSI = pH − pHs
pHs: pHs = (9.3 + A + B) − (C + D)
Where:
- A = (log10(TDS) − 1) / 10
- B = −13.12·log10(T(°C)+273) + 34.55
- C = log10(Ca hardness as CaCO₃) − 0.4
- D = log10(Alkalinity as CaCO₃)
Risk Score (0–100) is a weighted blend of hardness, alkalinity, pH, temperature, TDS,
operating concentration, irrigation intensity, filtration, and flushing interval.
How to use this calculator
- Enter recent water test values for hardness, alkalinity, pH, and TDS.
- Set temperature close to what flows through your lines.
- Estimate evaporation or concentration in storage tanks daily.
- Choose your system type and your current filter rating.
- Add your flushing interval and weekly irrigation frequency.
- Press Calculate to see risk, LSI, and actions.
Example data table
| Scenario | Hardness | Alkalinity | pH | Temp | TDS | System | Flush | Expected |
|---|---|---|---|---|---|---|---|---|
| Soft source water | 90 ppm | 60 ppm | 7.1 | 18°C | 280 ppm | Spray | 14 days | Low |
| Typical municipal | 260 ppm | 140 ppm | 7.6 | 25°C | 650 ppm | Drip | 14 days | Moderate |
| Hard well water | 650 ppm | 280 ppm | 8.2 | 30°C | 1400 ppm | Drip | 28 days | High |
Use the examples to sanity-check your inputs and expected risk band.