Showerhead Flow Rate
Average measured flow rate of all showerheads in the home. Alternative pathway: meet a Home Water Score threshold.
Spec by tier
This requirement steps in stringency by tier. Each tier inherits and tightens the value.
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
- 01.
Measure the flow rate (GPM) of every showerhead in the home, then calculate the average across all heads.
- 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.
- 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.
- 01.
Photo of each showerhead's manufacturer rating sticker or packaging showing rated GPM (and WaterSense label if applicable).
- 02.
OR a field flow-test record for each showerhead, including date, room location, measured flow rate, and inspector signature.
- 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:
- 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.
- 02.
Capture
Once steady-state flow is reached (3-5 seconds), start a timer and capture water for exactly 10 seconds.
- 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.
- 04.
Record
Record the result on the flow-test form along with the room/fixture identifier.
Resources
- EPA WaterSense — Showerhead specification →
Federal standard for high-efficiency showerheads (1.8 GPM at 80 psi, with spray-force and coverage minima).
- GreenHome Institute — Home Water Score →
The alternative scoring pathway referenced in the GreenStar spec.
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.