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Free Engineering Calculators

Water Softener Calculators

Size your softener resin vessel, optimize salt dose efficiency, and estimate hardness leakage at any exhaustion level — all client-side, no login.

1

Softener Sizing Calculator

Determine resin volume, vessel dimensions, salt per regeneration, brine tank size, and regeneration frequency.

Hardness units:
gpg
Enter in selected units above Required — enter a value ≥ 0
ppm
Soluble iron only; ≥ 0.5 ppm triggers pre-filter recommendation Enter a value ≥ 0
GPM
Required — enter a flow rate > 0
hours
Hours between regenerations (default: 24)
$/ton
Leave blank to skip annual cost estimate

Sizing Results

Effective Hardness: H_eff = H_in + 4 × Fe_ppm (gpg equivalent — iron counts as ~4× hardness for resin loading)

Grains per run: Q(GPM) × t_run(hr) × 60 × H_eff(gpg)

Resin capacity (kgrains/ft³): Linearly interpolated from AWWA-grade table for Standard Gel (6→17k, 8→20k, 10→22k, 12→24k, 15→27k) and High-Capacity (6→18.5k, 8→21.5k, 10→24k, 12→26k, 15→29k)

Resin volume: grains_per_run / (capacity_k × 1000)

Vessel sizing: SLR = 6 GPM/ft² → cross-sectional area = Q/6; diameter rounded up to nearest standard (0.75–3.0 ft)

Brine: Saturated brine ≈ 3.0 lbs NaCl/gal. Brine tank sized at 1.5× single regeneration salt requirement

2

Salt Efficiency Optimizer

Compare capacity, efficiency, and cost across all five salt dose levels to find the optimal operating point for your system.

ft³
Required — enter resin volume > 0
gpg
Required — enter hardness > 0
GPM
For run-length calculation
$/ton
For annual cost comparison

Salt Dose Comparison

Salt efficiency: capacity_kgrains/ft³ × 1000 / salt_dose_lbs/ft³ → grains per lb of salt

Service volume: total_capacity_kgrains × 1000 / H_in_gpg gallons treated per cycle

Run length: service_volume / (Q_gpm × 60) hours

Salt per 1,000 gal: salt_per_regen / service_volume × 1000

Best efficiency = highest grains/lb salt (lowest dose). Best capacity = highest total kgrains (highest dose). Optimal balance for most applications: 10 lbs/ft³.

3

Hardness Leakage Estimator

Estimate effluent hardness leakage as a function of resin exhaustion. Determine the maximum safe exhaustion before regeneration for your hardness target.

gpg
Required — enter hardness > 0
gpg
"Soft" water ≈ 0.5 gpg (8.5 ppm CaCO₃)
%
0% (fresh) 50% 100% (exhausted)

Real-Time Leakage Estimate

— gpg

Exhaustion level
50%

Leakage Analysis Results

Empirical leakage model — breakpoints (exhaustion → % of influent hardness as leakage):

0%→0%, 70%→2%, 75%→3%, 80%→8%, 85%→15%, 90%→25%, 95%→45%, 100%→100%

Linear interpolation between breakpoints.

Leakage (gpg): H_in × f(E) where f(E) is the interpolated fraction

Max safe exhaustion: binary search on f(E) to find E where leakage = target H_max

Model is empirical / indicative — actual breakthrough depends on resin condition, temperature, flow distribution, and regeneration quality.

Expert Analysis

Need a system design or performance audit?

These calculators handle the engineering math. When your softener system needs root cause analysis, program optimization, or an independent audit — that's where we come in.

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