WE: Indoor Water Use Reduction (Prerequisite + Credit)
Use less water first → then reuse water
Why This Matters
Indoor water use is one of the most controllable sources of water consumption in buildings.
👉 LEED focuses on:
Reducing fixture demand first → then using alternative water
🧩 Prerequisite vs Credit (Quick Comparison)
| Requirement | Prerequisite | Credit |
| Mandatory? | ✅ Yes | ❌ No |
| Points | 0 | Up to 6 |
| Reduction Required | ≥20% | 25%–50%+ |
| Alternative water allowed? | ❌ Not for first 20% | ✅ Yes (beyond 20%) |
🚿 WE Prerequisite: Indoor Water Use Reduction
Intent
👉 Reduce indoor potable water consumption
📏 Requirement
👉 Must achieve:
👉 ≥20% reduction from baseline
🚽 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 |
🧠 Exam Tip
👉 Memorize at least:
- 1.6 gpf (toilet)
- 1.0 gpf (urinal)
- 2.5 gpm (shower)
🚰 WaterSense Requirement
👉 Required for:
- Toilets
- Urinals
- Private lavatory faucets
- Showerheads
👉 Must be:
EPA WaterSense labeled
👥 Usage Assumptions (VERY TESTABLE)
👨👩👧 Occupancy Ratio
👉 50% male / 50% female
🚻 Daily Use Patterns
Women:
- 3 toilet flushes/day
Men:
- 1 toilet + 2 urinal uses/day
👉 This is used for:
- calculating baseline water use
- determining % reduction
⚠️ Critical Rule (EXAM TRAP)
👉 The first 20% reduction must come from:
- fixture efficiency
👉 NOT from:
- alternative water
💧 WE Credit: Indoor Water Use Reduction
Intent
👉 Go beyond prerequisite → deeper savings
📊 Points Structure
| Reduction | Points |
| 25% | 1 point |
| 30% | 2 points |
| 35% | 3 points |
| 40% | 4 points |
| 45% | 5 points |
| 50%+ | 6 points |
⚠️ Key Rule (VERY IMPORTANT)
👉 First 20% = efficiency only
👉 Beyond 20% = you may use:
- nonpotable water
- reuse systems
♻️ Nonpotable Water Sources
Projects may use:
- Reclaimed water
- Greywater
- Rainwater
- Stormwater
- Condensate (HVAC)
- Foundation dewatering water
- Seawater
- Process water
- Reverse osmosis reject water
🧠 Exam Insight
Alternative water is a bonus strategy, not a shortcut
🧠 Strategies to Reduce Indoor Water Use
🚿 1. Low-Flow Fixtures
- dual flush toilets
- ultra-low flow faucets
🚰 2. Efficient Appliances
- dishwashers
- clothes washers
📊 3. Submetering
- track usage
- identify inefficiencies
♻️ 4. Water Reuse Systems
- greywater reuse
- rainwater flushing
⚠️ Common Misconceptions
❌ “We can use rainwater to meet prerequisite”
👉 No
👉 First 20% must be from efficiency
❌ “All faucets have same baseline”
👉 No
👉 Public vs Private = different values
❌ “Urinals are optional in calculations”
👉 No
👉 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?
• reduces demand permanently
• ensures system resilience
• avoids dependence on supply systems
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