The EPA Exposure Factors Handbook (national survey data) gives about 869 mL a day per person across all ages, about 0.23 gallons, including water added to food and drinks. Adults average about 0.28 gallons; heavy drinkers (95th percentile) about 0.78. The EPA assumes 1 gallon a day when sizing RO systems. This is the number behind every yearly cost on this site.
| Source | What it found (quoted) and its limits | Evidence |
|---|---|---|
| US EPA WaterSense RO Supporting Statement (as C19): drinking & cooking assumption (2024) · new government technical document |
one gallon of permeate per person per day for drinking and cooking; household 2.57 persons; ~940 (938) gal permeate/household/yr Limits: Assumption, not measured; ~3.6x higher than EFH mean |
Evidence: strong Free to read · source · added 2026-10-30 |
| Vieux F, Maillot M, Rehm CD, Barrios P, Drewnowski A. Opposing Consumption Trends for Sugar-Sweetened Beverages and Plain Drinking Water: NHANES 2011-16. Front. Nutr. 7:587123 (2020) · new peer-reviewed NHANES analysis |
Plain water, age >30 y: 1,092 (2011-12), 1,106 (2013-14), 1,232 mL/day (2015-16); all ages >4 y: 1,144 mL/day (2015-16) Limits: Plain water only; tap/bottled split only in figures |
Evidence: strong Free to read · source · added 2026-10-30 |
| Rosinger AY, Herrick KA, Wutich AY, Yoder JS, Ogden CL. Disparities in plain, tap and bottled water consumption among US adults: NHANES 2007-2014. Public Health Nutr 21(8):1455-1464 (2018) · new peer-reviewed NHANES analysis |
"mean total plain water intake on a given day for US adults was 1167 (SE 26) ml"; "725 (SE 32) ml (62·2%) from tap water and 441 (SE 23) ml (37·8%) from bottled water"; 33.4% drank bottled water Limits: Plain drinking water only (no cooking); single 24-h recall |
Evidence: strong Free to read · source · added 2026-10-30 |
| DeOreo WB, Mayer P, Dziegielewski B, Kiefer J. Residential End Uses of Water, Version 2. Water Research Foundation (figures via Wikipedia summary) (2016) · new water-utility research foundation study |
indoor use "averaged 138 gphd"; "52.1 gpcd" at 2.65 persons/household; faucets 26.3 gal/household/day, "19 percent" of indoor use Limits: Read via secondary summary; WRF full report paywalled |
Evidence: strong Paywalled · source · added 2026-10-30 |
| US EPA. Exposure Factors Handbook, Chapter 3: Ingestion of Water and Other Select Liquids, Table 3-1 (NHANES 2003-2006) (2011 (posted 2019/2025)) · new government dataset/handbook |
Adults >=21 y per capita mean 1,043 mL/day, 95th pct 2,958 mL/day; consumers-only mean 1,227, 95th 3,092; all ages per capita mean 869, 95th 2,717; includes direct water and "water added to foods and beverages" during preparation; confidence "Medium to High" Limits: Community (tap) water only, excludes bottled; NHANES 2003-06 is old; 2-day recall |
Evidence: strong 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.