EPA's work for its WaterSense RO label puts typical systems at 10–20% efficiency, which means several gallons to drain for each gallon made. Newer and labeled models do far better. The US average water and sewer rate used by EPA is $15.21 per 1,000 gallons (2023).
| Source | What it found (quoted) and its limits | Evidence |
|---|---|---|
| US EPA WaterSense: Point-of-Use Reverse Osmosis Systems (product page; spec released Nov 2024) (2024) · new government programme page |
"a typical point-of-use RO system will generate five gallons or more of reject water for every gallon of treated water produced"; labeled systems "send just 2.3 gallons of water or less down the drain"; savings "more than 3,100 gallons of water per year" Limits: Programme estimate, not field-measured |
Evidence: strong Free to read · source · added 2026-10-30 |
| US EPA WaterSense. Supporting Statement for the Point-of-Use Reverse Osmosis Systems Specification (2024) · new government technical document |
"typical POU RO systems operate at efficiencies between 10 percent and 20 percent" (about 4-9 gal reject per gal); typical (15%) system: 5,320 gal reject/household/yr; WaterSense 30%: 2,190; "approximately one million POU RO systems are sold annually" Limits: Efficiencies are certification/lab-based; EPA states no data on installed base |
Evidence: strong Free to read · source · added 2026-10-30 |
| US EPA WaterSense Supporting Statement (as C19): water+sewer price assumption citing AWWA 2023 Water and Wastewater Rate Survey (Raftelis) (2024) · new government document citing industry survey |
$15.21 per thousand gallons average combined residential water and wastewater cost (AWWA 2023 Water and Wastewater Rate Survey, Raftelis); WaterSense RO saves "nearly $50 per year" Limits: National average hides 5x city variation; sewer often billed on winter average not marginal use |
Evidence: strong Free to read · source · added 2026-10-30 |
| AWWA Water & Wastewater Rate Survey (with Raftelis) - product page (2024-2026) · new industry rate survey (paywalled) |
"500 water and wastewater utilities across all 50 states contribute data" Limits: Paywalled; no averages on public page |
Evidence: strong Paywalled · source · added 2026-10-30 |
| US EPA WaterSense: Statistics and Facts (2015 data (page 2021-2025)) · new government |
"Each American uses an average of 82 gallons of water a day at home" (USGS 2015); "The average family spends more than $1,000 per year in water costs" Limits: Archived snapshot; 82 gpcd includes outdoor |
Evidence: strong Free to read · source · added 2026-10-30 |
| Bluefield Research. US water and sewer bill has increased 24% in five years (rate index press release) (2025) · new market research press summary |
Northeast "highest average combined water and sewer bills, totaling US$141.53 per month" (2024); South US$118.21/month; "a 24.1% increase in combined drinking water and sewer bills" 2019-2024; "61 utilities serving approximately 20% of the U.S. population" Limits: Usage volume behind bills not stated in summary; full index paywalled |
Evidence: moderate Free to read · source · added 2026-10-30 |
| Andrew R (NSF). RO Efficiency and Recovery. WC&P (2018) · new trade journal by standards body staff |
"the efficiency rating cannot be higher than the recovery rating"; "As the storage tank becomes more full, the efficiency rate of the system is reduced." Limits: Definitions only |
Evidence: moderate Free to read · source · added 2026-10-30 |
| Dvorak BI, Skipton SO. Drinking Water Treatment: Reverse Osmosis. NebGuide G1490, University of Nebraska-Lincoln Extension (rev.) (2014) · new university extension |
"Most household RO systems are designed with a 20 percent - 30 percent recovery rate"; membranes produce "in the range of 10 to 35 gallons per day" Limits: Design values, not measured; dated |
Evidence: moderate Free to read · source · added 2026-10-30 |
| UMass Amherst CAFE (adapted from URI). Reverse Osmosis Treatment of Drinking Water Supplies (2007) · new university extension |
"about 75 percent of the water introduced is wasted"; "four gallons of raw water into the system produce about one gallon of treated water"; one gallon takes "2-7 hours" Limits: Old (2007), generic |
Evidence: moderate Free to read · source · added 2026-10-30 |
| Circle of Blue 30-city water price survey, 2019 (as cited by Penn State EARTH 111 course) (2019) · new journalism survey via university course page (secondary) |
family of four "costing an average of $72.93 a month" "using an average of 100 gals/day each (12,000 gals/mo...)" Limits: Secondary citation; 2019; survey discontinued/archived; sewer inclusion unclear |
Evidence: weak Free to read · source · added 2026-10-30 |
| Cartwright P, Cartwright T. Recovery/Efficiency of RO Water POU Units: The Real Story. WC&P (2001) · new trade journal (engineering) |
recovery "usually between 10 percent and 30 percent"; worked example: tank back pressure cuts 25% design recovery to "18.3 percent" Limits: Illustrative calculation, no field dataset |
Evidence: weak Free to read · source · added 2026-10-30 |
| Aqua Flo CRO-800UX6 tankless RO specification sheet (MANUFACTURER CLAIM) (n.d.) · new manufacturer spec sheet (claimed) |
"(2 purified : 1 drain)"; "Recovery 65%"; "Power Used 120W"; flow "0.62 gal/min" Limits: Claimed recovery not efficiency; no certification listed; marketing |
Evidence: weak Free to read · source · added 2026-10-30 |
Evidence grade: strong = trials, large field studies or official datasets; moderate = smaller or lab studies with real water; weak = single small studies, makers' specs or secondary reports. "Free to read" means the source itself is free to read online.