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Ordering Information:
ORDER NUMBER: 90781
DATE AVAILABLE: Winter 1999/2000
(Also related, )
Printed Report |
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PRINCIPAL INVESTIGATORS:
Peter Mayer, William DeOreo, Eva Opitz, Jack Kiefer, William Davis, Benedykt
Dziegielewski, and John Olaf Nelson
OBJECTIVES:
Goals of this research included
- providing specific data on the end uses of water in residential settings
across North America
- assembling data on disaggregated indoor and outdoor uses
- identifying variations in water used for each fixture or appliance
- developing predictive models to forecast residential water demand
BACKGROUND:
The "end uses" of water include all the places where water is used
in a single-family home such as toilets, showers, clothes washers, faucets,
lawn watering, etc. Accurately measuring and modeling these end uses and the
effectiveness of conservation efforts has been the Achilles heel of urban water
planning for many years. Understanding where the consumer uses water is critical
information for utilities, planners, and conservation professionals. Empirical
evidence of the effectiveness of specific conservation measures can be used
to improve their design and provide justification for their continued support.
HIGHLIGHTS:
This report represents a time-and-place snapshot of water use in single-family
homes in 12 North American locations. Similarities and differences among "end
uses" were tabulated for each location, and were analyzed and summarized for
the entire group. The main findings include per capita usage for each identified
end use; savings available from indoor conservation measures; and predictive
models for indoor demand with a high transfer value for use by other utilities.
APPROACH:
Data collected from each of the 12 study sites included historic billing
records from a systematic random sample of 1,000 single-family detached residential
accounts; household information obtained through a mail survey sent to each
of the selected 1,000 households; approximately four weeks of specific data
on the end uses of water collected from a total of 1,188 households; supplemental
information including climate data; and information specific to each participating
utility. Data collection was divided into two, two-week intervals spaced in
time to attempt to capture summer (peak) and winter (off-peak, mostly indoor
water use) time frames.
Water consumption for various end uses was measured using compact data loggers
and flow trace analysis software. A flow trace is a record of flow through a
residential water meter recorded in 10-second intervals that provides sufficient
resolution to identify the patterns of specific fixtures within the household.
RESULTS/FINDINGS:
The mean annual water use for the 12 combined sites was 146,100 gallons
per household per year, with a standard deviation of 103,500 gallons and a median
of 123,200 gallons (n=12,075). Across all study sites, 42 percent of annual
water use was for indoor purposes and 58 percent for outdoor purposes. This
mix of indoor and outdoor uses was strongly influenced by annual weather patterns.
Daily Per Capita Use
Across all 1,188 study homes, the mean per capita indoor daily water use was
69.3 gallons (including leakage). Toilet use was estimated at 18.5 gallons per
capita per day (gpcd), clothes washer use was 15.0 gpcd, shower use was 11.6
gpcd, faucet use was 10.9 gpcd, leaks accounted for 9.5 gpcd, baths were 1.2
gpcd, dishwasher use was 1.0 gpcd, and other domestic use was 1.6 gpcd.
Ultra Low Flush (ULF) Toilet Savings
Of the over 289,000 toilet flushes recorded, 14.5 percent of the flushes were
less than 2.0 gallons per flush (gpf), 34.7 percent of the flushes were between
2 and
3.5 gpf, and 50.8 percent were greater than 4 gpf. It was found that 8.5 percent
of the homes used ULF toilets almost exclusively. These "ULF only" homes used
an average of 24.1 gallons per household per day (gpd) for toilet purposes.
The residents of these homes flushed the toilet an average of 5.04 times per
person per day and used an average of 9.5 gpcd. More than 65 percent of the
study homes did not use a ULF toilet. These "non-ULF" study homes averaged 47.9
gpd for toilets. Residents in these homes flushed an average of 4.92 times per
person per day and used an average of 20.1 gpcd. The net potential savings when
comparing "ULF only" homes from this study to the "non-ULF" homes is therefore
10.5 gpcd.
Low Flow (LF) Shower Savings
So-called "low flow" shower heads are designed to restrict flow to a rate of
2.5 gpm or less. About 15 percent of the study homes showered in the low-flow
range exclusively, 60.4 percent occasionally showered in the low-flow range,
and 24.5 percent showered exclusively above the low-flow range. The LF shower
homes used an average of 20.7 gpd and 8.8 gpcd for showering, while the non-LF
shower homes used an average of 34.8 gpd and 13.3 gpcd. However, the duration
of the average shower in the LF shower homes was 8 minutes and 30 seconds, whereas
the average shower duration in the non-LF homes was 6 minutes and 48 seconds.
IMPACT:
This study may impact the water industry in the following ways:
- Variability of water use in single-family sector. A tremendous variability
of use exists and may change the way utilities think about and analyze demand
patterns.
- Conservation potential.Developing targeted conservation programs is
important. Because many existing efficiencies exist in homes, broad-based
conservation programs will not be as successful as those that can identify
customers who can save the most water.
- Important new technique for evaluating demands. The flow trace analysis
technique represents a significant breakthrough in demand measurement. Utilities
can take advantage of the vital information about customer usage that this
technique harnesses.