Water Efficiency Calculator

No -- and this is a structural property of the math, not a rounding coincidence. Water Savings (%) is (baseline use minus proposed use) divided by baseline use, and both the baseline and proposed use figures are multiplied by the exact same Occupants and Workdays per Year before that ratio is taken, so those two factors cancel out completely. They still fully determine the gallon totals (Baseline Use, Proposed Use, Annual Savings) and the dollar figure (Annual Cost Savings) -- just not the percentage.

Toilet GPF, because toilet flushing is the largest baseline water-use category per person in this calculator's usage assumptions (up to 3 flushes/day for female occupants). A given proportional improvement to toilet efficiency moves Water Savings (%) more than the same proportional improvement to urinal, lavatory, or showerhead flow.

It changes how baseline and proposed water use are split between toilets and urinals, since the calculator assumes female occupants flush toilets 3 times/day while male occupants flush 1 time/day plus 2 urinal uses. A higher Male Occupant Ratio shifts weight toward the urinal-inclusive usage pattern, which does change Water Savings (%) because it doesn't cancel the way total occupant count does.

Because Occupants and Workdays per Year are essential for every gallon-based and dollar-based output -- Baseline Use, Proposed Use, Annual Savings (gal), and Annual Cost Savings all scale directly with them. Only the percentage figure and the LEED points derived from it are unaffected, since those are ratios where the occupancy scaling cancels out.

They're the real federal fixture flow-rate standards set by the Energy Policy Act of 1992 (EPAct 1992): 1.6 gallons per flush for toilets, 1.0 gallon per flush for urinals, 2.2 gallons per minute for lavatory faucets, and 2.5 gallons per minute for showerheads. This calculator's default proposed-fixture values -- 1.28 GPF, 0.5 GPF, 0.5 GPM, and 2.0 GPM -- correspond to the EPA WaterSense program's labeled maximum flow rate for each fixture type (WaterSense's lavatory faucet limit is 1.5 GPM; the 0.5 GPM default here represents an even more efficient "ultra-low" faucet), so the calculator's out-of-the-box comparison is a real WaterSense-vs-EPAct-1992-baseline scenario, not an arbitrary one.