Water Efficiency
What the category covers
WE reduces potable water use indoors, outdoors, and in cooling towers. Prerequisites in v4 BD+C: Outdoor Water Use Reduction, Indoor Water Use Reduction, and Building-Level Water Metering. Credits add points for deeper reductions and for cooling tower and submetering strategies.
Concepts to know
- Baseline fixture rates (v4, at 60 psi): water closet 1.6 gpf, urinal 1.0 gpf, lavatory 0.5 gpm, showerhead 2.0 gpm, kitchen sink 2.2 gpm. Reductions are calculated from these, weighted by daily uses and occupancy.
- Outdoor prerequisite: reduce irrigation demand (or use no potable irrigation); the credit pushes further, with no potable irrigation being the top tier.
- Cooling tower: maximize cycles of concentration and use nonpotable makeup water where available.
- Submetering: separate meters for irrigation, indoor fixtures, cooling tower, and process water so leaks and waste are visible.
Traps
- A 20% reduction satisfies the prerequisite; anything at or above that earns credit tiers - do not confuse the two thresholds.
- Reductions must be calculated from the baseline, not from the local code, unless the code is more stringent.
- Sewer or process water savings are handled separately; do not fold them into the indoor fixture calculation.
- Occupancy assumptions must be consistent across credits.
Worked example
A project replaces 1.6 gpf toilets with 1.28 gpf models and keeps everything else at baseline. Weighted across total flush volume, that alone rarely reaches 20% - pair it with 0.5 gpm lavatories at lower flow and 1.0 gpf urinals. Rule of thumb: a uniform 20% cut below every baseline fixture is the simplest way to clear the prerequisite with margin.