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Water Treatment Water Savings Estimator

The Water Treatment Water Savings Estimator estimates how much external water demand can be displaced when treated water is reused for a defined daily demand. It compares usable treated-water availability with the reuse demand, applies the number of operating days per year, and optionally converts the saved volume into avoided water-purchase cost.

This is useful for facilities evaluating non-potable reuse, process-water recirculation, irrigation supply, or other applications where treated water substitutes for water that would otherwise be purchased or withdrawn. The limiting principle is simple: annual savings cannot exceed either the reuse demand or the treated-water volume available for that use. The cost figure is therefore a planning value based on the entered water rate, not a full lifecycle economic analysis.

Water-offset estimate

gal/day
gal/day
days/yr
$/1k gal
Result
—
Annual water savings
Daily water offset—
Annual cost avoided—
Demand covered—

1. Enter the reuse demand
Provide the daily volume that could accept treated water.

2. Enter treated-water availability
Use the daily amount that is actually available for the reuse application.

3. Set annual operating days
Count only the days when both the treatment system and reuse demand are expected to operate.

4. Add an avoided water rate
Enter the external water cost per 1,000 gallons if you want a cost-avoidance estimate.

5. Compare savings and coverage
Review annual gallons saved, daily offset, cost avoided, and the percentage of demand covered.

Annual water savings = min(Reuse demand, Treated water available) × Operating days

Where:

  • Reuse demand: eligible demand in gallons per day
  • Treated water available: usable treated-water supply in gallons per day
  • Operating days: days per year when substitution occurs
  • Avoided cost: annual savings ÷ 1,000 × water rate

Assumption: The calculation assumes every gallon counted as available can directly replace an external-water gallon and does not include seasonal mismatch, storage losses, or treatment downtime beyond the entered operating-day assumption.

What the result means

The main result is a planning estimate derived directly from the entered operating assumptions and should be interpreted within the stated system boundary.

Use project-specific design criteria, equipment data, and applicable requirements before making final engineering or procurement decisions.

Given:

  • Reuse demand = 30,000 gal/day
  • Treated water available = 24,000 gal/day
  • Operating days = 330 days/year
  • Avoided water rate = $6.50 per 1,000 gal

Calculation:
Daily offset = min(30,000, 24,000) = 24,000 gal/day.
Annual savings = 24,000 × 330 = 7,920,000 gal/year.
Cost avoided = 7,920 × $6.50 = $51,480.

Result:
7,920,000 gallons per year, with about $51,480 of avoided water cost.

The treated-water supply covers 80% of the stated reuse demand on operating days.

Why does the calculator use the smaller daily value?

Water savings are constrained by both demand and supply. Extra treated water cannot create additional savings when there is no matching reuse demand, and unmet demand cannot be offset without enough treated water.

Should I enter total facility demand or only reusable demand?

Enter only the portion that can legitimately be supplied by the treated water being evaluated. Uses that require a different water quality should remain outside the reuse-demand input.

How should seasonal operation be handled?

Use operating days to represent the period when reuse actually occurs. For strongly seasonal systems, separate season-by-season calculations can be more representative than one annual average.

Does avoided cost include sewer or energy charges?

Not automatically. The rate field is a single avoided water rate, so include only charges you intentionally want represented on a per-1,000-gallon basis.

How is this different from recovery rate?

Water savings measures external demand displaced over time; recovery rate measures the fraction of feed water converted into usable treated product.