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Water Efficiency & Management

Zero Water Capable

Home is plumbed and equipped to operate without municipal water inputs (rainwater + greywater + on-site treatment).

Zero Water Capable (placeholder seal) ZWC PLACEHOLDER

Description

The Zero Water Capable badge recognizes homes that are plumbed, treated, and equipped to operate without any municipal water input — drinking, bathing, and irrigation all met by on-site sources (rainwater catchment, greywater reuse, and where applicable on-site groundwater) with appropriate treatment.

"Capable" rather than "Certified" is intentional: the home must demonstrably be able to run off-grid for water, but does not need to prove a 12-month period of zero municipal use. Many projects earning this badge maintain a municipal connection for redundancy or fire-suppression code reasons and operate primarily on captured water.

A related Home Water Score-based pathway exists in the GreenStar standard: achieving a Home Water Score of 10 earns the closely-related "Zero Water Certified" recognition through fixture and landscape efficiency alone (without requiring rainwater infrastructure). Zero Water Capable goes further by requiring the supply infrastructure itself.

Required standard requirements

To earn this badge, the project must meet all of the following existing GreenStar requirements:

Additional badge criteria

Beyond the required standard requirements above, the project must also satisfy:

On-site supply & treatment

  1. 01.

    Rainwater catchment system sized to meet 100% of annual indoor potable demand based on local average annual rainfall, roof catchment area, and modeled household demand (occupants = bedrooms + 1, per the GHI Home Water Score convention).

  2. 02.

    Potable treatment train rated for the captured supply: minimum first-flush diverter + sediment filter + carbon filter + UV disinfection + NSF/ANSI 53/55-certified components. Storage cistern food-grade or NSF 61 rated.

  3. 03.

    Greywater system reusing bath/shower/laundry effluent for toilet flushing and/or sub-surface irrigation, designed per local code (typically Uniform Plumbing Code Chapter 16 or IAPMO 326).

  4. 04.

    Backup pathway documented: either a properly disconnected municipal connection (with backflow prevention) or a documented well-water tie-in. Storage volume sized for at least 30 days of typical demand during dry periods.

Demand reduction

  1. 01.

    Project must also achieve a Home Water Score ≥ 5 (Gold tier) — captured supply only works at meaningful scale once fixture demand is cut.

  2. 02.

    No conventional flush toilets above 1.0 GPF. Composting or vacuum toilets count toward the demand reduction and are encouraged.

  3. 03.

    Outdoor irrigation served exclusively by greywater, captured rainwater, or drought-adapted plantings with no supplemental irrigation.

Documentation

  1. 01.

    Water-balance calculation showing annual supply (captured + reused) ≥ annual modeled demand, with 30-day reserve.

  2. 02.

    Plumbing permit + sign-off from local AHJ for the rainwater and greywater systems.

  3. 03.

    Water-quality test results from the potable supply at first occupancy: pH, turbidity, total coliform, E. coli, and (where applicable) lead and nitrate.

  4. 04.

    Photos of the catchment surface, cistern, treatment skid, and greywater diverter / surge tank.

Verification by tier

Evidence the project team submits at each certification tier. Cumulative — higher tiers include everything below unless noted otherwise.

  1. Certified

    Self-attestation
    • 01.

      Owner-signed water-balance worksheet: annual catchment volume vs annual modeled demand, with the 30-day reserve calculation.

    • 02.

      Photos of the catchment surface, cistern, treatment skid, and greywater diverter.

  2. Silver

    Documents + photos
    • 01.

      Plumbing permit + AHJ sign-off for the rainwater and greywater systems.

    • 02.

      Manufacturer cut sheets for storage cistern (NSF 61) and treatment-train components (NSF 53 / 55).

  3. Gold

    Third-party test
    • 01.

      Potable water-quality test from a state-licensed lab at first occupancy: pH, turbidity, total coliform, E. coli (and lead / nitrate where applicable).

    • 02.

      Third-party plumbing inspection of cross-connection isolation and backflow prevention.

  4. Platinum

    Post-occupancy verification
    • 01.

      12-month water meter log showing municipal supply use trending to zero (or documented disconnect from municipal supply with maintained reserve).

    • 02.

      Annual water-quality re-test for as long as the badge is claimed.

Water Efficiency & Management Required from Certified Zero Water Capable Home Water Score

Showerhead Flow Rate

Average measured flow rate of all showerheads in the home. Alternative pathway: meet a Home Water Score threshold.

Spec by tier

TierSpec
Certified≤ 2.2 GPM average — or Home Water Score of 2
Silver≤ 2.0 GPM average — or Home Water Score of 3
Gold≤ 1.5 GPM average — or Home Water Score of 5
Platinum≤ 1.25 GPM average — or Home Water Score of 6

Scope

All showerheads installed in the dwelling unit, including primary, guest, and accessory bathrooms. Hand-held wands count as part of the fixture they share a valve with. Bathtub spouts and tub-only fillers are excluded.

Requirements

Performance targets

  1. 01.

    Measure the flow rate (GPM) of every showerhead in the home, then calculate the average across all heads.

  2. 02.

    The average GPM must meet the tier threshold shown in the "Spec by tier" table above. Hand-held wands are measured separately and included in the average.

  3. 03.

    Alternative pathway: the project may submit a Home Water Score report meeting the tier threshold in lieu of per-fixture measurement.

Documentation

Evidence the inspector / Institute will need.

  1. 01.

    Photo of each showerhead's manufacturer rating sticker or packaging showing rated GPM (and WaterSense label if applicable).

  2. 02.

    OR a field flow-test record for each showerhead, including date, room location, measured flow rate, and inspector signature.

  3. 03.

    OR a completed Home Water Score report referencing the dwelling and showing the required score.

Guidance

Why flow rate matters

Showerheads are typically the second-largest indoor water draw after toilets, and they pull from the water heater — so cutting shower flow saves both water and the energy used to heat it. EPA WaterSense estimates a typical household saves ~2,700 gallons of water and 330 kWh of electricity per year by switching from a 2.5 GPM head to a 1.5 GPM WaterSense head.

Field flow-test procedure

When the manufacturer rating is missing or you want field verification:

  1. 01.

    Set up

    Hold a graduated 1-gallon flow bag (or a calibrated container) under the showerhead. Turn the shower on full hot and full cold so the mixing valve runs at the same total flow it would in normal use.

  2. 02.

    Capture

    Once steady-state flow is reached (3-5 seconds), start a timer and capture water for exactly 10 seconds.

  3. 03.

    Calculate

    Divide the captured volume (gallons) by 10, then multiply by 60 to get GPM. Example: 0.25 gal in 10 sec × 6 = 1.5 GPM.

  4. 04.

    Record

    Record the result on the flow-test form along with the room/fixture identifier.

Resources

Note

WaterSense ratings are measured at 80 psi static pressure. Actual field flow at lower house pressures (most homes run 40-60 psi) may be lower than the sticker value, which is fine — the spec accepts the manufacturer rating as the documented value.

Example — Averaging across fixtures

A 4-bathroom home has showerheads rated at 1.5, 1.5, 1.8, and 1.5 GPM. The average is 1.575 GPM — passes Silver (≤ 2.0) and Gold (≤ 1.5? No, 1.575 > 1.5). To clear Gold, the 1.8 GPM head would need to be swapped for one ≤ 1.0 GPM, or all four upgraded to 1.5 GPM caps.

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Water Efficiency & Management Required from Certified Zero Water Capable Home Water Score

Bathroom Aerator Flow Rate

Average measured flow rate of all bathroom faucet aerators.

Spec by tier

TierSpec
Certified≤ 2.0 GPM average — or Home Water Score of 2
Silver≤ 1.75 GPM average — or Home Water Score of 3
Gold≤ 1.0 GPM average — or Home Water Score of 5
Platinum≤ 0.5 GPM average — or Home Water Score of 6

Scope

Aerators on every bathroom lavatory (sink) faucet in the dwelling. Kitchen, utility, and laundry-sink aerators are excluded.

Requirements

Performance targets

  1. 01.

    Measure or read the rated flow rate (GPM) of every bathroom faucet aerator in the home.

  2. 02.

    Calculate the average GPM across all bathroom aerators; the average must meet the tier threshold in the "Spec by tier" table.

  3. 03.

    Alternative pathway: submit a Home Water Score report meeting the tier threshold in lieu of per-fixture measurement.

Documentation

Evidence the inspector / Institute will need.

  1. 01.

    Photo of each bathroom aerator showing the stamped GPM rating (typically printed on the underside or on the packaging).

  2. 02.

    OR field flow-test record (date, location, measured GPM, signature) for each aerator.

  3. 03.

    OR a Home Water Score report referencing the dwelling.

Guidance

How to read an aerator

Bathroom aerators are stamped with their flow rate in tiny letters on the underside, on the side ring, or on the original packaging. The most common ratings are 0.5, 1.0, 1.5, 2.0, and 2.2 GPM. WaterSense-labeled aerators max out at 1.5 GPM and produce noticeably softer spray.

Swapping a non-compliant aerator

Most aerators swap in under a minute with no tools:

  1. 01.

    Unscrew

    Unscrew the existing aerator by hand (counterclockwise as you look up at it). If it is stuck, wrap with a rag and use slip-joint pliers gently.

  2. 02.

    Match thread

    Bathroom aerators come in male (M22 or M24) and female (M22x1) thread. Bring the old one to the store to match.

  3. 03.

    Install

    Hand-tighten the replacement with the included washer. No tools or thread tape required.

  4. 04.

    Test

    Run full flow for 10 seconds and re-measure to confirm.

Resources

Note

For Platinum, the 0.5 GPM target is aggressive but workable in bathrooms (faucets are used mostly for short hand-washing bursts). Kitchen faucets generally cannot run that low and are not covered by this requirement.

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Water Efficiency & Management Required from Certified Zero Water Capable Home Water Score

Toilet Flush Volume

Average flush volume across all toilets in the home.

Spec by tier

TierSpec
Certified< 1.6 GPF average — or Home Water Score of 2
Silver< 1.3 GPF average — or Home Water Score of 3
Gold≤ 1.0 GPF average — or Home Water Score of 5
Platinum< 1.0 GPF average — or Home Water Score of 6

Scope

Every toilet installed in the dwelling unit, including dual-flush models. Bathtubs, urinals (residential only), and bidets are excluded.

Requirements

Performance targets

  1. 01.

    Identify the rated GPF (gallons per flush) for every toilet in the home. For dual-flush toilets, use the higher of the two flush volumes (full flush) for compliance calculations.

  2. 02.

    Calculate the average rated GPF; the average must meet the tier threshold in the "Spec by tier" table.

  3. 03.

    Alternative pathway: submit a Home Water Score report meeting the tier threshold.

  4. 04.

    New construction at Silver and above must install only toilets meeting the tier threshold — averaging in older fixtures is not permitted on new builds.

Documentation

Evidence the inspector / Institute will need.

  1. 01.

    Photo of each toilet's manufacturer rating (cast or printed on the bowl behind the seat or on the underside of the tank lid) showing GPF.

  2. 02.

    OR completed measurement record (bucket-and-stopwatch method) for each toilet.

  3. 03.

    OR Home Water Score report.

Guidance

How dual-flush counts

For a 1.6/1.1 GPF dual-flush toilet, GreenStar counts the 1.6 GPF full flush — not a weighted average. The rationale is that occupants do not always select the appropriate flush, so the standard assumes worst-case usage. Single-flush 1.28 GPF WaterSense toilets typically outperform dual-flush models on this basis.

Retrofit options

For existing toilets above the threshold: (a) replace the toilet with a WaterSense unit, (b) install an adjustable dual-flush conversion kit (some are accepted by GHI; verify with the inspector before relying on this), or (c) install a tank fill-cycle diverter / displacement bag to reduce flush volume — last-resort, only useful for marginal cases.

Resources

Example — Averaging a mixed home

A 3-toilet home has units rated 1.6, 1.28, and 1.28 GPF. The average is 1.387 GPF — passes Certified (<1.6) but fails Silver (<1.3). Swapping the 1.6 GPF unit for a 1.28 brings the average to 1.28 — passes Silver and Gold (≤1.0? No, 1.28 > 1.0).

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Water Efficiency & Management Required from Certified Zero Water Capable Home Water Score

Plumbing Leak & Pressure Test

Pressure test the plumbing system; no leaks permitted. Documented via the LEED-format Water Pressure and Leak Verification Report.

Scope

All cold- and hot-water supply piping inside the dwelling envelope, from the point of entry (meter or well pressure tank) through every fixture connection.

Requirements

  1. 01.

    Pressurize the supply system per local plumbing code (typically 60-100 psi static or 1.5× working pressure, whichever is higher).

  2. 02.

    Hold the test pressure for the code-required duration (commonly 15 minutes for the basic test) with all fixtures closed.

  3. 03.

    Pressure must hold with zero observable drop. Any pressure loss requires the leak to be located and repaired before retesting.

  4. 04.

    On new construction, the test must be performed before drywall is closed in over the supply lines.

Documentation

Evidence the inspector / Institute will need.

  1. 01.

    Completed LEED-format Water Pressure and Leak Verification Report (or equivalent) signed by the plumber or GreenHome Inspector.

  2. 02.

    Photo or scan of the pressure-test gauge at start and end of the hold period (if available).

Guidance

Why it matters

A single 1/16-inch supply-line leak behind drywall can waste 15+ gallons per day and cause thousands of dollars in moisture damage before being noticed. The pressure test is the single most cost-effective failure check in residential plumbing.

Field procedure

Most plumbers run this as part of rough-in. For existing-home retrofits:

  1. 01.

    Isolate

    Shut off all fixtures and close the main shutoff temporarily; open one fixture briefly to confirm system pressure has not fluctuated.

  2. 02.

    Gauge

    Attach a pressure gauge at the outdoor hose bib or a service tee. Note the static pressure.

  3. 03.

    Hold

    Re-pressurize and observe the gauge for the required hold period. A drop of even 1-2 psi indicates a leak.

  4. 04.

    Locate

    If pressure drops, isolate sections (hot vs. cold, upper vs. lower floors) by closing intermediate valves and re-running to narrow down the location.

Note

Pressure tests do not catch slow leaks at fittings under normal operating pressure that only show up under thermal cycling. Bath fan and water-leak inspections during the moisture assessment cover those.

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Water Efficiency & Management Required from Gold Zero Water Capable

Cold-Water Pipe Insulation

Insulate cold-water pipes, or keep them out of unconditioned space.

Scope

Cold-water supply lines running through any unconditioned space (attics, crawlspaces, exterior walls in cold climates, garages, vented soffits).

Requirements

  1. 01.

    Insulate all cold-water supply lines passing through unconditioned space with closed-cell foam pipe sleeves of R-3 minimum (commonly 3/8" or 1/2" wall thickness).

  2. 02.

    OR route all cold-water supply lines through conditioned space only, eliminating exposure to unconditioned conditions.

Documentation

Evidence the inspector / Institute will need.

  1. 01.

    Photos of insulated cold-water runs showing foam sleeve coverage at joints, tees, and elbows.

  2. 02.

    OR marked-up architectural drawings showing all cold-water lines routed through conditioned space (acceptable for new construction).

Guidance

Why insulate cold lines (not just hot)

Two reasons: (1) prevents condensation / "sweating" on cold pipes during humid weather, which can drip into wall cavities and cause hidden moisture damage; (2) reduces freeze risk in cold climates where pipes pass through unconditioned space. The energy savings are minor compared to hot-water insulation, but the moisture-management benefit is significant.

Note

Pair cold-water insulation with R-3+ hot-water insulation on the same runs. Hot-water insulation is a baseline expectation and reduces standby losses by 4-9% per the DOE.

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Water Efficiency & Management Required from Gold Zero Water Capable

Tap Water Filtration

Install tap-water filtration appropriate to local water-quality conditions.

Scope

The primary drinking-water tap (typically the kitchen sink cold tap). Whole-house filtration is acceptable but not required.

Requirements

  1. 01.

    Obtain or request the local Consumer Confidence Report (CCR) from the water utility, or — for well water — perform a current water-quality test.

  2. 02.

    Install a point-of-use or whole-house filtration system rated to remove the specific contaminants flagged in the CCR or well test.

  3. 03.

    At minimum, the filter must hold an NSF/ANSI 42 certification (aesthetic — chlorine, taste, odor) for treated municipal water. NSF/ANSI 53 (health-related: lead, cysts, VOCs) or 401 (emerging contaminants) is required where those contaminants are present.

Documentation

Evidence the inspector / Institute will need.

  1. 01.

    Copy of the CCR or well water-quality test results highlighting contaminants of concern.

  2. 02.

    Filter specification sheet showing matching NSF/ANSI certifications.

  3. 03.

    Photo of installed filter with model number visible.

Guidance

Reading a CCR

Every U.S. public water utility publishes an annual Consumer Confidence Report listing detected contaminants and their levels relative to the MCL (maximum contaminant level). Items at or near MCL — especially lead, chromium-6, nitrates, disinfection byproducts (TTHMs), PFAS — should drive the filter selection.

Filter types

Pitcher / faucet-mount filters meet the spirit of the requirement only if certified for the specific contaminants. Under-sink activated-carbon block units (e.g. Multipure, AquaTru, Berkey countertop) are typically the highest-performing point-of-use option. Whole-house systems are appropriate only for chlorine and sediment — they do not effectively remove dissolved metals or PFAS.

Resources

Note

Filter cartridges have a finite life — typically 6-12 months for carbon, 5-10 years for reverse osmosis membranes. Document the replacement cadence in the building maintenance instructions.

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Water Efficiency & Management Required from Platinum Zero Water Capable Resilience Home Water Score

Water Leak Detection & Real-Time Metering

Real-time water leak detection and metering system installed.

Scope

Whole-home plumbing — the system must monitor the entire supply line for unusual flow patterns indicative of a leak.

Requirements

  1. 01.

    Install a whole-home water monitoring + leak detection system at the main supply line (post-meter, pre-distribution).

  2. 02.

    System must provide real-time flow data accessible via mobile app or web interface.

  3. 03.

    System must detect anomalous flow (continuous flow exceeding a threshold, indicating a likely leak) and alert the occupant within 1 hour.

  4. 04.

    Automatic water shutoff capability is strongly recommended but not required (alert-only systems are acceptable).

Documentation

Evidence the inspector / Institute will need.

  1. 01.

    System specification sheet (Flo by Moen, Phyn Plus, Sense Save, etc.) showing real-time metering + alert capability.

  2. 02.

    Photo of the installed unit at the main supply line.

  3. 03.

    Screenshot of the occupant's mobile app showing live data from the unit.

Guidance

Auto-shutoff vs alert-only

Auto-shutoff systems (Flo, Phyn Plus) close the main water valve when a leak is detected — they prevent damage even if the occupant ignores the alert. Alert-only systems (Sense Save, Streamlabs) are cheaper but rely on the occupant acting promptly. For Platinum-level homes, auto-shutoff is the better fit even though the requirement is permissive.

Pair with point sensors

Whole-home meters detect supply-line leaks but miss drain-side issues (washer drain backup, toilet overflow). Add inexpensive Wi-Fi water sensors under sinks, behind toilets, near the water heater, and in the laundry pan. Most whole-home systems pair with these as a unified alerting system.

Note

Many insurance carriers (Travelers, Liberty Mutual, Nationwide) offer 3-15% homeowner premium discounts for installed leak detection. Have the homeowner submit the device certification to their carrier after installation.

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