Water Use: The
IN REU2016, APPROXIMATELY 1,000 single-family
residential accounts were
randomly selected from each
of 23 study sites (Figure 5).
Billing records showed average annual per household
water use ranging from
44,000 to 175,000 gallons per
household per year (gphy).
The “Other” category includes evaporative cooling, humidification, water softening, and other uncategorized indoor uses.
Figure 1. Indoor household use by fixture
The large range in use reflects the strong
influence of climate and weather patterns.
Agencies participating in this study come
from across the United States and Canada
and encompass a tremendous geographic
and climactic diversity. Outdoor use is
more variable than indoor use, and homes
in warmer climates have higher outdoor
use, continuing to irrigate in winter.
to the declines in residential water use.
REU2016 showed indoor water use at 138
gallons per household per day (gphd). A
sample of new homes built according
to EPA’s WaterSense New
Home Specification Version
1.0 had an average daily per
household water use of 110
gphd (DeOreo et al. 2011).1
uses like landscape irrigation, water used
through hose bibs, water for filling and
backwashing swimming pools, water for
washing pavement and cars, and so forth.
A fundamental goal of REU2016 was to
quantify how much water is used both
indoors and outdoors, as well as per capita
and per household. Such metrics are valuable for understanding water use patterns,
establishing efficiency levels, and developing predictive models of future demand.
While the average annual
use for all sites (23,749
homes) was 88,000 gphy,
the Landscape Group’s
annual use averaged
101,000 gphy, of which outdoor use constituted 50%,
or 50,500 gphy.
TOILET FLUSHING IS the largest indoor
use of water in single-family homes, followed by showers, faucets, clothes washers, leaks, other/miscellaneous, bathtubs,
and dishwashers (Figure 1).
IN A SUB-SAMPLE of 94
homes, the average household hot water use was 45.5
gphd, which accounted for
33.2% of total indoor water
use. Showers and faucets
each consumed substantially more hot water than
all the other end uses combined. For showers, the
average daily household hot
water use was 17.8 gallons,
and for faucets, 15.4 gallons.
use the most
water of any
sector. The 23
show a decline of
22% in average
use since WRF’s
use when mak-
ing future plans
Mandated reductions in toilet flush
and clothes washer volumes, and shower
and faucet flow rates, have contributed
OUTDOOR WATER USE was
studied more extensively in REU2016
than REU1999, specifically, the efficiency
of landscape irrigation. The Landscape
Group was comprised of a sample of
838 homes selected as a representative
subset from participating water utilities.
Local weather conditions, irrigated area,
water cost, and type of plant material are
major drivers of outdoor use. The outdoor
water use category is comprised of water
To analyze outdoor
water use, the estimated
actual use was compared
to the theoretical irrigation requirement—an
estimatoin of water needs
for residential and park
landscapes. The theoretical irrigation requirement
is considered the amount
of irrigation that is theoretically required, although
many landscapes can thrive
on a lesser amount.
The majority of study
1Nearly 100% of the 25 new homes
studied in DeOreo et al. 2011 met
the following efficiency criteria:
clothes washers with capacities of
≤ 30 gallons per load, shower flow
rates ≤ 2.5 gallons per minute, and
toilet flushes ≤ 2.0 gallons per flush.
participants (72%) applied considerably
less water than was theoretically required
and were termed “low/deficit irrigators.”
Sixteen percent of study participants were
considered“target” irrigators, because they
applied close to the theoretical irrigation
requirement. A small group of over-irriga-tors applied gross excess water compared
to the estimated theoretical requirement.