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<Proceedings of the International Symposium on Efficient Water Use in Urban Areas - Innovative Ways of Finding Water for Cities -> RESIDENTIAL END USES OF WATER by “We have met the enemy and he is us.” “Every man is his own chief enemy.” RESIDENTIAL END USES OF WATER Introduction: In 1996 the American Water Works Association (AWWA) Research Foundation embarked on a research project entitled “The North American Residential End Uses of Water Study” (REUWS). Cosponsoring the study were a number of regional agencies, states and fourteen cities. Twelve study sites were targeted across North America: the cities of Boulder and Denver in Colorado; Eugene, Oregon; Seattle, Washington; the City of Lompoc and San Diego in California and special water districts serving Walnut Valley and Las Virgenes, California; the City of Tampa, Florida; City of Phoenix, Arizona; the neighboring cities of Scottsdale and Tempe, Arizona which were treated as one study site; and the neighboring Canadian cities of Waterloo and Cambridge, Ontario which were also treated as one study site. Site characteristics are shown in Table 1. The research team was lead by Aquacraft, Inc., Colorado, 80302, www.Aquacraft.com (William DeOreo, Peter Mayer), the principle contractor who collected water use data and performed data logging and analysis; Planning and Management Consultants Ltd., Carbondale, Illinois, www.PMCL.com (Eva Opitz, Benedykt Dziegielewski, Jack Kiefer and William Davis ) handled sampling, survey design, model analysis and statistics; and John Olaf Nelson Water Resources Management was responsible for customer surveys and project quality assurance and quality control. The final report has been submitted for publication by AWWARF and will be available later this year. The report and comprehensive database will be available on CD ROM from AWWARF, 6666 Quincy, Denver, CO. The database, a rich resource of residential water use information, is prepared in Microsoft ACCESS and includes 28,000 daily use records, 38,700 daily weather records, 1.96 million end use event records, 6,000 survey response records, and 39 weather station identity records. Tables are cross linked with a Keycode to protect individual customer privacy. Purpose of Research: The purpose of this project was to identify typical end uses of water in single family detached homes for the participating water utilities. This need had been identified as the highest urban water conservation research priority at a special workshop held by the Water Conservation Division of AWWA in 1993. While not intended to be utilized to represent a typical picture of residential water use for all of North America, the surprisingly stable indoor water use portion does lend itself to being combined for comparative purposes. Research Strategy: The research strategy was to identify a representative sample of single family detached homes in each of the 12 study sites, survey a representative sample of these to determine information from the customer, and select a representative sample for data logging in winter and summer months. The initial sample of representative homes in each study site numbered 1,000 dwellings. A comprehensive survey form containing 41 questions was mailed to this sample. The response rate ranged from 38% to 66% with a mean of 48%. From survey respondents, 100 homes were selected for data logging. Water use of the parent population, the 1,000 representative sample, and the 100 data log sample was calculated and statistical checks made at each step to assure the validity of each sample. Data logging involved installing a relatively small battery operated data-logger manufactured by F.S. Brainard and Company, Burlington, New Jersey in the meter box and strapping a transducer to the magnetic type meter head. For two weeks in the summer and two weeks in the winter, the average flow rate passing through the meter was recorded every 10 seconds. Software developed by Aquacraft called Trace Wizard© was then used to identify individual end use events, i.e. a gravity toilet refill cycle, clothes washer cycle, shower event, bath event, irrigation system cycle, faucet event, leakage, etc. Each type of event is unique and can be graphically represented by a trace (see Figures 1 through 4 for examples of different traces). Trace types also varied from home to home (different clothes washing machines, shower habits, etc. Once characteristic traces were determined for a given home, the software then automatically searched the entire logging record collected for that home and identified and segregated end uses of water. The software was capable of segregating 99% of all events successfully. The event categories were: bath, clothes washer, dish washer, faucet, irrigation system, toilet, evaporative cooler, hot tub, humidifier, treatment system (generally a water softener), swimming pool, leak and unknown. Heretofore physical measurement of residential end uses has been limited to a few very expensive (and intrusive) micro-metering studies involving very small samples. Over 1.9 million event records were measured for the 1,188 logged homes in the REUWS. Other data was also collected: metered water consumption from utility billing records, weather data, water and sewer rates and data on water conservation programs and efforts. Results: Survey data revealed the statistics shown in Table 2. A total of 28,015 days of 10 second interval data was collected from the 1,188 homes. Average daily water use was 1,548 Liters per day (Lpd) [409 gallons per day (gpd)] with a standard deviation of 1,840 Lpd (486 gpd). The indoor fraction was 655 Lpd (173 gpd) and had a standard deviation of 356 Lpd (94gpd). Indoor use was much less variable than outdoor use. Ninety percent of indoor use was less than 1,136 Lpd (300 gpd) on average. Total per capita use for the 12 study sites averaged 650.3 Liters per capita per day (Lcd) (171.8 gcd) with 381.5 Lcd (100.8 gcd) or 58.7% coming from outside use, 6.4 Lcd (1.7 gcd) or 1% unknown and 262.3 Lcd (69.3 gcd) or 40.3% from indoor use. Standard deviation for indoor use was 161.3 Lcd (42.6 gcd). Median indoor use was 227.5 Lcd (60.1gcd). Mean indoor use varied by 99.9 Lcd (26.4 gcd). Median indoor use varied by 48.8 Lcd (12.9 gcd), about half as much. Typical distribution of indoor household water use is shown in Figure 5. Frequency of fixture utilization is shown in Table 3. The leakage amount includes outside leaks since these could not readily be separated from indoor leaks. The Trace Wizard analysts opined, however, that the lions share of leakage could be attributed to leaking toilets - principally flapper valves. Regards the surprisingly high average leak rate of 36.0 Lcd (9.5 gcd), analysis revealed that nearly 60% of leakage volume was explained by only 10% of the logged homes. Costs: The total budget for the project was $881,000 with $530,000 in cash from AWWARF and the government agencies and utilities plus $288,000 of in-kind contributions (mainly in the form of labor) from the utilities. The average cost per home based on the 1,188 logged homes was therefore $742. Each home was logged a total of four weeks. Since this was a pioneering research effort, considerable time was donated to the project by the consultant team over and above the budget amount. This is estimated at $200,000. The true cost to conduct the study is therefore estimated at $910 per logged home. Estimated cost of future logging efforts, including initial analysis, sample size determination, survey work, field logging and analysis and report is shown in Table 4. The technology employed in REUWS can readily be employed in any metered community around the world to determine end uses of water. The technique is equally successful in determining end uses for most small commercial sites as well provided coincident occurrences of the same type of event are infrequent. Characterization of end use of water is essential to sound formulation and conduct of an effective water conservation program. DEMAND MANAGEMENT OPPORTUNITIES Research of the literature and application of the findings of the REUWS has been performed by the author (go www.waterwiser.org/wtruse98/main.html) and reveals opportunities for demand management. This is not new information, but the level of accuracy is certainly enhanced over prior literature on the subject. As shown in Figure 5, we now have very accurate data on the distribution of residential indoor end uses. From the data collected in the REUWS, an improved estimate of unit water savings for household water using fixtures was made - see Table 5 for details and Table 6 for recap. Improved estimates on typical penetration of ultra low-flush toilets and low-flow shower heads is also possible (Table 7). Application of these values indicates that the amount of existing indoor savings achieved to date by long term water conservation efforts, based on the sample analyzed in the REUWS, is 12.2 Lcd (3.2 gcd) which means typical indoor use had likely achieved a level of 274.5 Lcd (72.5 gcd) prior to the conservation efforts of the late 1970's, 80's and 90's. Calculation of indoor end uses of water both for the “without” and “with” case based on conservation technology now commonly available is shown in Table 8. Figure 6 shows the comparison graphically. The result is that for the typical single family home in North America, indoor water use (without any conservation fixtures) of on the order of 274.5 Lcd (72 .5 gcd) can be expected to drop by 32% to 187.8 Lcd (49.6 gcd) given technologies now in hand. The differential is 86.7 Lcd (22.9 gcd). Of this amount, it appears that 12.2 Lcd (3.2 gcd) of savings or 14% has already been accomplished. This leaves plenty of room for improvement. Principal indoor opportunity targets are toilets, clothes washers, shower heads, faucet aerators and leak repair. Whether retrofit strategies are justified for a given water utility depends on the avoidable costs and other factors unique to that utility. To the extent that fixtures commonly used in North America are used in Asia, development of baseline information on end uses of water as described in the first section of this paper and implementation of regulations and cost-effective strategies targeting the opportunities outlined in the second section of this paper, makes good sense.
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