WE: Indoor Water Use Reduction (Prerequisite + Credit)
Use less water first โ then reuse water
Why This Matters
Indoor water use is one of the most controllable sources of water consumption in buildings.
๐ LEED focuses on:
Reducing fixture demand first โ then using alternative water
๐งฉ Prerequisite vs Credit (Quick Comparison)
| Requirement | Prerequisite | Credit |
| Mandatory? | โ Yes | โ No |
| Points | 0 | Up to 6 |
| Reduction Required | โฅ20% | 25%โ50%+ |
| Alternative water allowed? | โ Not for first 20% | โ Yes (beyond 20%) |
๐ฟ WE Prerequisite: Indoor Water Use Reduction
Intent
๐ Reduce indoor potable water consumption
๐ Requirement
๐ Must achieve:
๐ โฅ20% reduction from baseline
๐ฝ Baseline Fixture Flow Rates (VERY IMPORTANT)
| Fixture | Baseline (IP) | Baseline (SI) |
| Toilet (Water Closet) | 1.6 gpf | 6 lpf |
| Urinal | 1.0 gpf | 3.8 lpf |
| Public Lav Faucet | 0.5 gpm | 1.9 lpm |
| Private Lav Faucet | 2.2 gpm | 8.3 lpm |
| Kitchen Faucet | 2.2 gpm | 8.3 lpm |
| Showerhead | 2.5 gpm | 9.5 lpm |
๐ง Exam Tip
๐ Memorize at least:
- 1.6 gpf (toilet)
- 1.0 gpf (urinal)
- 2.5 gpm (shower)
๐ฐ WaterSense Requirement
๐ Required for:
- Toilets
- Urinals
- Private lavatory faucets
- Showerheads
๐ Must be:
EPA WaterSense labeled
๐ฅ Usage Assumptions (VERY TESTABLE)
๐จโ๐ฉโ๐ง Occupancy Ratio
๐ 50% male / 50% female
๐ป Daily Use Patterns
Women:
- 3 toilet flushes/day
Men:
- 1 toilet + 2 urinal uses/day
๐ This is used for:
- calculating baseline water use
- determining % reduction
โ ๏ธ Critical Rule (EXAM TRAP)
๐ The first 20% reduction must come from:
- fixture efficiency
๐ NOT from:
- alternative water
๐ง WE Credit: Indoor Water Use Reduction
Intent
๐ Go beyond prerequisite โ deeper savings
๐ Points Structure
| Reduction | Points |
| 25% | 1 point |
| 30% | 2 points |
| 35% | 3 points |
| 40% | 4 points |
| 45% | 5 points |
| 50%+ | 6 points |
โ ๏ธ Key Rule (VERY IMPORTANT)
๐ First 20% = efficiency only
๐ Beyond 20% = you may use:
- nonpotable water
- reuse systems
โป๏ธ Nonpotable Water Sources
Projects may use:
- Reclaimed water
- Greywater
- Rainwater
- Stormwater
- Condensate (HVAC)
- Foundation dewatering water
- Seawater
- Process water
- Reverse osmosis reject water
๐ง Exam Insight
Alternative water is a bonus strategy, not a shortcut
๐ง Strategies to Reduce Indoor Water Use
๐ฟ 1. Low-Flow Fixtures
- dual flush toilets
- ultra-low flow faucets
๐ฐ 2. Efficient Appliances
- dishwashers
- clothes washers
๐ 3. Submetering
- track usage
- identify inefficiencies
โป๏ธ 4. Water Reuse Systems
- greywater reuse
- rainwater flushing
โ ๏ธ Common Misconceptions
โ โWe can use rainwater to meet prerequisiteโ
๐ No
๐ First 20% must be from efficiency
โ โAll faucets have same baselineโ
๐ No
๐ Public vs Private = different values
โ โUrinals are optional in calculationsโ
๐ No
๐ Male usage assumptions must be included
Official FAQs
What is the minimum reduction required for the prerequisite?
What is the baseline flow rate for toilets?
A project achieves 18% reduction using efficient fixtures. Does it comply?
Must reach 20%
A project uses rainwater to achieve 25% reduction but only 10% comes from efficient fixtures. Does it comply?
First 20% must be efficiency
Why does LEED require efficiency before alternative water?
โข reduces demand permanently
โข ensures system resilience
โข avoids dependence on supply systems
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