Water Hardness & Softener Dosage Calculator

ANA›Life Services Authority›National Calculator Authority›Water Hardness & Softener Dosage Calculator

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Water Hardness & Softener Dosage Calculator

Calculate your water hardness classification and determine the precise water softener salt dosage required to treat your water supply effectively.

Water Hardness Value

Hardness Unit

ppm (mg/L as CaCO₃) gpg (grains per gallon) °dH (German degrees) °fH (French degrees)

Daily Water Usage (litres/day)

Softener Salt Type

Sodium Chloride (NaCl) — Rock/Solar Salt Sodium Chloride (NaCl) — Evaporated Salt Potassium Chloride (KCl)

Ion Exchange Resin Capacity (L)

Target Softened Hardness (ppm)

Calculate

function watCalc() { // --- Grab inputs --- const rawHardness = parseFloat(document.getElementById('wat-hardness-value').value); const hardnessUnit = document.getElementById('wat-hardness-unit').value; const dailyLitres = parseFloat(document.getElementById('wat-flow-rate').value); const saltType = document.getElementById('wat-softener-type').value; const resinVol = parseFloat(document.getElementById('wat-resin-capacity').value); const targetPpm = parseFloat(document.getElementById('wat-target-hardness').value); const resultDiv = document.getElementById('wat-result');

// --- Validation --- const errors = []; if (isNaN(rawHardness) || rawHardness 0 litres)."); if (isNaN(resinVol) || resinVol 0 litres)."); if (isNaN(targetPpm) || targetPpm 0) { resultDiv.style.display = 'block'; resultDiv.innerHTML = '' + errors.map(e => '').join('') + ''; return; }

// --- Unit conversion to ppm (mg/L as CaCO3) --- // 1 gpg = 17.118 ppm // 1 °dH = 17.848 ppm // 1 °fH = 10.000 ppm let conversionFactor = 1; let unitLabel = 'ppm'; if (hardnessUnit === 'gpg') { conversionFactor = 17.118; unitLabel = 'gpg'; } if (hardnessUnit === 'dH') { conversionFactor = 17.848; unitLabel = '°dH'; } if (hardnessUnit === 'fH') { conversionFactor = 10.000; unitLabel = '°fH'; }

const hardnessPpm = rawHardness * conversionFactor; // ppm as CaCO3

// --- Hardness classification (WHO / WQA scale) ---
let classification = '';
let classColor = '';
if (hardnessPpm 0)
? resinCapacityGrains / dailyGrainsLoad: Infinity; daysBetweenRegen = Math.min(daysBetweenRegen, 30); // cap at 30 days practical max

// --- Salt dosage per regeneration --- // Industry standard: NaCl requires ~0.3 kg salt per 1000 grains removed (efficient regeneration) // KCl requires ~0.35 kg per 1000 grains (slightly less efficient) // Evaporated NaCl: same as NaCl but higher purity assumed (0.28 kg/1000 grains) let saltKgPer1000Grains = 0.30; let saltName = 'Sodium Chloride (Rock/Solar)'; if (saltType === 'nacl_evap') { saltKgPer1000Grains = 0.28; saltName = 'Sodium Chloride (Evaporated)'; } if (saltType === 'kci') { saltKgPer1000Grains = 0.35; saltName = 'Potassium Chloride'; }

const saltPerRegen = (resinCapacityGrains / 1000) * saltKgPer1000Grains; // kg per regeneration

// --- Monthly salt usage ---
const regensPerMonth = (daysBetweenRegen > 0 && isFinite(daysBetweenRegen))
? 30 / daysBetweenRegen: 0; const monthlySalt = regensPerMonth * saltPerRegen; // kg/month

// --- Brine solution volume needed per regeneration --- // Standard brine concentration: 26% NaCl by weight (saturated ~315 g/L) // Volume of brine = saltPerRegen (kg) / 0.315 (kg/L) const brineConc = (saltType === 'kci') ? 0.270 : 0.315; // kg/L saturated const brineVolume = saltPerRegen / brineConc; // litres

// --- Waste water per regeneration --- // Typical ion exchange regeneration uses ~40–60 L per litre of resin const wasteWater = resinVol * 50; // litres (midpoint estimate)

// --- Format helpers --- const fmt = (n, d=2) => isFinite(n) ? n.toFixed(d) : '—'; const fmtDays = isFinite(daysBetweenRegen) ? daysBetweenRegen.toFixed(1) : '> 30';

// --- Output --- resultDiv.style.display = 'block'; resultDiv.innerHTML = ` ### Results

Water Hardness Analysis

Input Hardness ${rawHardness} ${unitLabel}

Converted Hardness ${fmt(hardnessPpm, 1)} ppm | ${fmt(hardnessGpg, 2)} gpg

Classification ${classification}

Target Softened Hardness ${targetPpm} ppm (${fmt(targetGpg, 2)} gpg)

Hardness to Remove ${fmt(removalGpg, 2)} gpg

Softener Performance

Resin Exchange Capacity ${fmt(resinCapacityGrains, 0)} grains

Daily Hardness Load ${fmt(dailyGrainsLoad, 0)} grains/day

Days Between Regenerations ${fmtDays} days

Regenerations per Month ${fmt(regensPerMonth, 1)}

Salt & Brine Dosage (${saltName})

Salt per Regeneration ${fmt(saltPerRegen, 2)} kg

Monthly Salt Usage ${fmt(monthlySalt, 2)} kg/month

Annual Salt Usage ${fmt(monthlySalt * 12, 1)} kg/year

Brine Volume per Regeneration ${fmt(brineVolume, 1)} litres

Estimated Waste Water per Regeneration ${fmt(wasteWater, 0)} litres

${hardnessPpm = 60 ? '⚠ Target hardness equals or exceeds source hardness. Adjust your target value.

' : ''} `; }

#### Formulas Used

Unit Conversions to ppm (mg/L as CaCO₃):

Resin Capacity (grains): Capacity = Resin Volume (L) × 45,000 mg CaCO₃/L ÷ 64.799 mg/grain

Daily Hardness Load (grains/day): Load = (Source Hardness − Target Hardness) [gpg] × Daily Usage [US gal/day]

Days Between Regenerations: Days = Resin Capacity [grains] ÷ Daily Load [grains/day]

Salt Dosage per Regeneration: Salt (kg) = (Resin Capacity ÷ 1,000) × Salt Factor Salt factors: NaCl Rock/Solar = 0.30 kg/1,000 grains; NaCl Evaporated = 0.28 kg/1,000 grains; KCl = 0.35 kg/1,000 grains

Brine Volume: Brine (L) = Salt (kg) ÷ Saturated Brine Concentration (NaCl: 0.315 kg/L; KCl: 0.270 kg/L)

#### Assumptions & References

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