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Calcimator

Water Efficiency Calculator

Calculate indoor water use savings from efficient fixtures compared to EPA baseline for LEED WEc2 credit analysis.

Inputs

%

Results

Water Savings (%)

39.2%

Baseline Use (gal/yr)80,938
Proposed Use (gal/yr)49,188
Annual Savings (gal)31,750
LEED WEc2 Points3
Cost Savings ($/yr)$191.00
How to Use This Calculator
  1. Enter Number of Occupants (FTEs) and Workdays Per Year for the building.
  2. Enter fixture flow rates: Toilet GPF, Urinal GPF, Lavatory Faucet GPM, and Showerhead GPM.
  3. Enter Male Occupant Ratio percentage for combined toilet/urinal usage calculations.
  4. Review Water Savings percentage vs EPA baseline and Annual Savings in gallons.
  5. Check LEED WEc2 Points earned and Annual Cost Savings to quantify the financial benefit.

How the result changes with Toilet (GPF)

Toilet (GPF)Water Savings (%)
0.854.1%
1.5530.9%
2.453.1%
3.2-20.1%

What each input means

Number of Occupants (FTEs)
Full-time equivalent occupants in the building.
Workdays per Year
Number of occupied days per year. Commercial: 250, residential: 365.
Toilet (GPF)
Proposed toilet gallons per flush. WaterSense: 1.28, dual-flush: 1.1/1.6, high-eff: 1.0.
Urinal (GPF)
Proposed urinal gallons per flush. Standard: 1.0, WaterSense: 0.5, waterless: 0.
Lavatory Faucet (GPM)
Proposed lavatory faucet flow rate. Baseline: 2.2, WaterSense: 1.5, ultra-low: 0.35-0.5 GPM.
Showerhead (GPM)
Proposed showerhead flow rate. Baseline: 2.5, WaterSense: 2.0, low-flow: 1.5 GPM.
Male Occupant Ratio (%)
Percentage of male occupants (affects toilet vs urinal usage calculations).

What each result means

Water Savings (%)
Percentage reduction in indoor water use vs EPA baseline.
Baseline Use (gal/yr)
Annual indoor water use with EPA baseline fixtures.
Proposed Use (gal/yr)
Annual indoor water use with your proposed efficient fixtures.
Annual Savings (gal)
Total gallons saved per year compared to baseline.
LEED WEc2 Points
Points earned for Indoor Water Use Reduction (0-6 points).
Cost Savings ($/yr)
Estimated annual water and sewer cost savings.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Number of Occupants (FTEs) = 50, Workdays per Year = 250, Toilet (GPF) = 1.28, Urinal (GPF) = 0.5 = 7 input(s) provided
  2. Calculate Water Savings
    39.2 = 39.2%
  3. Calculate Baseline Use
    Baseline Use = baselineDailyPerPerson * occupants * workdaysPerYear
    80938 = 80938
  4. Calculate Proposed Use
    Proposed Use = proposedDailyPerPerson * occupants * workdaysPerYear
    49188 = 49188

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.

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