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The Water Economy of a Low Flush Toilet in a Water Deficient Region Albert E. Pratt Technical Report No. 3 July 1979 WATER RESOURCES RESEARCH CENTER Caribbean Research Institute College of the Virgin Islands St. Thomas, United States Virgin Islands The Water Economy of a Low Flush Toilet in a Water Deficient Region. By Albert E. Pratt Water Resources Research Center Caribbean Research Institute College of the Virgin Islands St. Thomas, USVI 00801 Contract No. A—004-VI Research Period 3/77 to 9/78 A project completion report. July 1979 The work upon which this report is based was supported by funds provided by the United States Department of the Interior, Office of Water Research and Technology as authorized under the Water Resources Act of 1964, P.L. 88- 379. Technical Report No. 3 Water Resources Research Center Caribbean Research Institute College of the Virgin Islands St. Thomas, USVI 00801 ABSTRACT Water use at public restroom facility was substantially reduced after installation of lo-f1ush toilets. 1ater in the region j scarce, demand is high, and water is epensiye. The first year of operation of the low-flush toilets saved 36,500 gallons and reduced the true cost of water used at the facility predominately desal ted wafer, frolT 757 to S210. The research dirnonstratect the practical value of a conservation technique that, If widely used in the Territory, could substantially reduce costs for government water and energy production, CONTENTS PAGE LIST OF FIGURES Vi LIST OF TABLES Vii INTRODUCTION 1 OBJECTIVES 2 SCOPE 2 APPROACH AND METHODS 2 RESULTS AND DISCUSSION 3 Public School Use 7 Overnight Accornmodations Use 8 Government Office IJse 8 Public Housing Use 8 Residentia1 Use 8 RECOMENDAT1ONS 9 ACKNOWLEDGEMENTS 10 LITERATURE 11 TABLES 12 APPENDIX A 19 LIST OF FIGURES Page Record of Water Use at Red Hook 4 LIST OF TABLES Page 1. Water Center Water Meter Records 12 2. Comparison of Water Use Records for the Red Hook Facility 13 3. Installation of Low-Flush Toilets at Red Hook. 14 4. Public Works Department; Jan. 1976-Dec. 1976 15 5. Public Works Department; Jan. 1977-Dec. 1977 16 6. Public Works Department; Jan. 1978—Sept. 1978 17 7. Public Works Department; Oct. 1978-May 1979 18 INTRODUCTION AND OVERVIEW The Territory of the U.S. Virgin Islands is composed of three main islands: St. Croix (84 sq. mi.), St. Thomas (28 sq. mi.), and St. John (20 sq. mi.), and more than 60 smaller islands and cays. The islands as a group receive an average of 40 inches of rainfall annually; however, about 90 percent of that rainfall is lost to evapotranspiration and the group of tropical, oceanic islands is classified as being semi-arid. The water resources, therefore, are scarce and generally of poor quality. Because of the limited scale of each island, there is no hinterland from which to draw additional resources. Approximately 100,000 people live on the land area of 135 square miles. Most of the population relies directly on roof catchment and cistern storage of the inconstant rainfall for household water supplies. The Territory experienced a period of phenomenal economic growth and population expansion during the 1960’s and 1970’s. The government invested heavily lb sea water desalting plants in an attempt to relieve the chronic short supply of potable water created by the demands of a booming tourism-based economy. Temporarily successful in fulfilling the needs for potable water, by the mid-70’s operational failures of the desalting equipment in combination with a continual reliance on inefficient and obsolete distribution systems and the meteorically rising price of energy made it impossible for the government to meet daily potable water needs, and a six-hour per day rationing schedule was imposed on public water supplies. At peak production, the desalting p1ant are capable of supplying approximately 75% of the estimated peak daily demand of 5.5 million gallons of potable water for the Territory. Present cost for desalting sea water is assumed to be at least $15 per thousand gallons; the true cost of production for the V.1. Water and Power Authority is not known. The water is distributed to the public by the Virgin Islands government (Public Works Department) and consumers are charged a rate of $4 per thousand gallons, making it necessary for the government to substantially subsidize Territorial water supply programs. Conservation of water has therefore been identified as one of the ways the Virgin Islands government can reduce the strain of the present fiscal squeeze. The Virgin Islands Water Resources Research Center, through a grant from the U.S. Department of Interior, Office of Water Research and Technology, installed several low—flush toilets in a heavily trafficked public restroom facility on St. Thomas and monitored the performance of those units for a period of seventeen (17) months. The project served a practical use for the residents and visitors of the Territory and demonstrated the conservation and cost-saving potential of .such equipment to the public agencies that operate and service the public restroom facility. OBJECTIVES The project was intended to measure a reduction in water usage at a public restroom facility after installation of law-flush toilets, monitor maintenance and operational problems, and evaluate, the net effects that wide—scale use of low—flush equipment could have on the present lve1 of demand for government water production and distribution. SCOPE The installation of 1ow-flush toilets in combination with a monitoring program provided the opportunity to evaluate the effects of reducing the amount of water required for sanitary flushing on: a) the daily water needs for operating specific restroom facility,, b) Territory-wide water needs by projecting a reduction of demand, and c) reducing the cost of water for an average household in the U.S Virgin Islands. APPROACH AND METHODS Five (5) conventional toilets in a public restroom facility at Red Kook Ferry Dock, St. Thomas were replaced with low— flush toilets at a total cost of$358O. The facility is operated by the V.1. Ports Authority and was selected as the project site because it serves the needs of the many residents of St. John and St. Thomas as well as tourists who regularly use the St. Thomas-St John ferries. Water for the facility is supplied without cost to the Ports Authority by the Public Works Department. Water is trucked as needed from the public standpipe in Sub-base, about twelve miles away, and is stored at the, site in a 1,000 gallon steel tank. It is then pumped to the restroom for use in the lavoratories and for sanitary flushing. The low-flush units that were installed were Microphor LF- 310 stainless steel toilets. The system requires 50 to 70 PSI of compressed air and a small amount of water from gravity flow or, as in this project, at 1-60 PSI. A push button mounted on the toilet activates a flow of water into the bowl and opens a valve in the base of the toilet. The valve is then closed automatically and a charge of compressed air ejects waste materials into a discharge line. The Microphor unit is designed to operate on two (2) quarts of water per flush. All parts of the unit are corrosion resistant, a beneficial feature because of the high level of chlorides present in most of the water delivered to the facility. A water meter was installed in the feed line between the storage tank and the restroom. The newly-completed installation was tested cm February 24, 1977. From 7:30 a.m. until 3:15 p.m. there was a total of 60 flushes of the units and 30 gallons of water was used. A conventional toilet would have required more than 300 gallons for the identical use. Operation of the facility was monitored for a period of seventeen (17) months, from February 24, 1977 to June 22, 1978. Water delivery records were submitted for analysis by the Public Works Department for the period January 1, 1976 to June 30, 1979. RESULTS AND DISCUSSION The theoretical reduction of the water used for sanitary flushing at the Red Hook facility is a factor of at least 10:1. The 10:1 reduction is the result of replacing the conventional flush toilets which require five (5) gallons (or more) per flush with units that require only two (2) quarts (or, 0.5 gallons) of water per flush. In order to test the performance of the retrofitted facility, data was aggregated by reporting calendar quarters. Four quarters of the research period were then isolated for which good comparisons of the data could be made. The analysis period selected was from April 1977 through March 1978. During the analysis period, the Public Works Department records show that a total of 14,000 gallons of water was delivered to the Red Hook facility: a total of 50,500 gallons was delivered for the corresponding period one year earlier. No count was made of the number of people using the facility and no records of previous levels of use exist. For purposes of this study, it was assumed that traffic patterns were similar for the years 1976- 1978. (Note: Maintenance personnel noted that there appeared to be an increase in traffic during the research period, and that it was probably due to the improvement of the facility.) FIG. 1 Record of Water Use at Red Hook PROJECT NO. A-004-VI The Water Economy of a Low-flush Toilet Calendar Quarters Gallons The actual reduction of water use recorded by the government for the analysis period was a ratio of 3.6:1-- representing a savings of 36,500 gallons of water. At $4 per thousand gallons, the cost of providing water to the Red Hook facility was reduced from $202 to $56 a savings of $156 in one year. If the water savings is computed at the assumed true cost of water for the Virgin Islands government-- $15 per thousand gallons—-the reduction was $757.50 to $210.00, or a true savings of $547.50. The measurements of the performance of the low-flush toilets by records from water meter readings also reflect the significant savings during the research period. Discrepancies between sets of data are assumed to be caused by the paucity o-F reliable means for government to measure and monitor deliveries of water in the Territory. Analysis of the water meter records reveals that a total of 12,660 gallons of water was used at the facility for the analysis period (April 1977 - March 1978). The facility used an average of 30.4 gallons per day for the analysis period, and 32.7 gallons per day for the duration of the project (2/24/77 6/22/78). This computes to an average use of 60-65 flushes per day with the Microphor units. A conventional flush toilet (5 gallons/flush, or more) would require 300-325 gallons of water per day for that level of use. During the course of the project, electrical problems were experienced with the compressor unit. It was found that it was a deficiency in the facility wiring and was corrected by the Ports Authority. One mechanical breakdown occurred with a toilet unit. Replacements of a malfunctioning valve cost $70, the total expenditure for maintenance and repair during the research period. A simple calculation to compute the rate of amortization of the investment in the low-flush toilets would be: Annual cost of operating conventional toilets - Annual cost of operating low—flush toilets = Annual Savings then, Total Investment Annual Savings Rate of Amortization (in number of years) A computation for the Red Kook facility based on a water price of $4 per thousand gallons is: Conventional Unit (5 gal/flush) 65 flushes/day x 5 gallons x 365 x $4/1000 = $475.50 Low-Flush Unit (0.5 gal/flush) 65 flushes/day x 0.5 gal x 365 x $4/1000 = 47.45 Gross Annul Savings: $427.05 Less adjustment for annual maintenance & repair 50.00* Adjusted Gross Annual Savings: $377.05 *Note: It is assumed that the amount of electricity required to operate the compressor balances the amount normally required to operate the water pump--in fact, the energy demand should be lessened because the low- flush units require less water to be pumped for the same level of use. The total cost for the installation of low-flush-toilets at the Red Hook facility was $3580. Based on the present level of use, and at a price for water at $4 per thousand gallons, it will take.9.5 years to amortize the investment. A computation for the Red Hook facility based on the assumed true cost of water ($1511000) in the Virgin Islands is: Conventional Unit 65 x 5 x 365 x $15/1000 = $1779.38 Low—Flush Unit 65 x 0.5 x 365 x $15/1000 = 177.94 Gross Annual Savings $1601.44 Less Adjustment 50.00 Adjusted Gross Annual Savings $1551.44 Based on the true cost of water to the government, it will actually take only 2.3 years to amortize the Red Hook investment. The experience of the installation and use of low-flush toilets in St. Thomas demonstrates the level of conservation of water that can be attained by the practical applications of such devices. It has also demonstrated that low-flush toilets, though more expensive to purchase than is a conventional toilet, can quickly pay for itself in the savings that can be realized where water is scarce and expensive. Clearly, there are many immediate applications in the U.S. Virgin Islands for conserving water and saving money by installing low— flush toilets, particularly with the true cost of water as high as $15 per thousand gallons. With very few assumptions and several general calculations, some of the more obvious applications for low—flush toilets with maximum benefit to the government of the Virgin Islands can easily be identified. First, the assumptions: a) The peak daily demand in the U.S. Virgin Islands is 5.5 million gallons of potable water; the true cost (production, storage, debt service, distribution, administration, etc.) to the government is $15 per thousand gallons; therefore, water costs each resident of the Territory 82.5 per day, or, a total of $30.1 million annually for the government. b) Typically, 45% of all residential and commercial water (not including industrial) is used for sanitary flushing (Note: This is an accepted standard.); for reasons peculiar to water-scarce areas such as the Virgin Islands, this amount may be less; say, an average of 35% for flushing. c) The Microphor low-flush toilets theoretically save 90% of the water which would be used by a conventional toilet; there are various low-flush toilets available commercially, and if in use, will save various amounts of water; say, an average savings of 50%. Therefore, if 35% of the peak daily demand for potable water is used for sanitary flushing, it costs the residents of the Territory $10.5 million per year to flush toilets. However, if all toilets were water savers, it would cut the cost in half: assuming the average price for a low—flush toilet is $300, the money saved by the government would purchase more than 17,000 toilets each year: The fact is, no one is really sure how much water is used or needed in the Territory. No one knows how much money, public or private, is invested in water annually. What is clear is that water saved is also energy and money saved. Reduci1g the amount of water used correspondingly reduces the energy required to desalt sea water, operate pumps in our homes as well as the public distribution system, distribute water by trucks on congested streets and highways, and to collect and treat waste water. Where can low-flush toilets be installed most easily to maximize the impact on water demands in the Territory? Public School Use: The present school population is estimated to be 26,000. Assuming each student flushes a conventional toilet 1.5 times a day (5 gall flush), the water used is 195,000 gallons/day. At a true cost of $15/1000 gallons, the water costs $2925.’ Assuming the school year is 180 days, water used simply for sanitary flushing in schools costs the government $526,500 each year. Assuming low-flush toilets were installed throughout the school system and 50% of the flushing water was saved, 877 low-flush toilets could be paid for with public funds that now go down the drain in one year. Overnight Accommodations Use: (Hotels, Guesthouses, etc.) There are presently 4300 units in the U.S. Virgin Islands. Assuming an occupancy rate of 2.5 people per unit and each guest uses 100 gallons/day--45% of which is for sanitary flushing--a total of 483,750 gallons of water is used each day for flushing. Assuming an annual occupancy rate of 30%, 53 million gallons of water are required by overnight visitors to the islands for sanitary flushing each year. If half of the water is saved by using low-flush toilets, approximately 1324 toilets could be purchased by money saved the first year. (Note: A recent installation of low-flush toilets at a beach hotel on St. Thomas reduced overall consumption of water from over 100 gpcd to 80 gpcd.) Government Office Use: It is estimated that there is a total employment of 40,000 and that 25% (or 10,000) of those jobs are part of the local (Territorial) government sector. Assuming that each employee flushes a conventional toilet twice a day, the water used for flushing totals 100,000 gallons and costs the government $1500/day. In one year, assuming each employee works 200 days, water for sanitary flushing costs the government $300,000. If half of the water was saved by installing low—flush toilets in all government offices, 500 toilets could be paid for in the first year of operation. Public Housing Use: The V.I. Housing Authority owns about 15% of the housing stock in the Territory and shelters approximately 18% (or 180OO) of the population. Assuming that water use is 35 gallons per person per day and that 25% of that total is used for sanitary flushing, approximately 57.5 million gallons is required annually for flushing toilets (or, 157,500 gallons per day). The true cost of that water is $862,500. If low-flush toilets were installed throughout the public housing units, 1437 toilets could be paid for with the first year’s savings on water purchases. Residential Use: Most households in the Virgin Islands depend almost exclusively on roof catchment and cistern storage of rainfall for water supply. It has been estimated that the true cost of cistern water (i.e. capital investment in cistern, amortization, operation of pumps, maintenance, etc.) is $20 per thousand gallons. It is assumed that water use in households on cisterns averages 50 gallons’per capita per day. A family of four would therefore use about 73,000 gallons per year. Assuming each resident flushes a conventional toilet twice a day, 14,600 gallons (or, 20%) of the cistern supply is used for sanitary flushing purposes at a cost of approximately $290/year. If a $400 low-flush toilet was installed, it would take slightly less than three years to amortize the investment. Since most households in the Territory are not serviced by central sewer service, and since most of the soils throughout the Territory are poorly drained, an additional benefit derived from decreasing the amount of water used for sanitary flushing is that ground waters would be less affected by contamination from poorly operating household septic systems. And finally, decreasing all sources of wastewater by decreasing the amount of water used for sanitary flushing will help protect the marine environments surrounding these islands--a resource that is immeasurably important to the well—being of the inhabitants of the Virgin Islands. RECOMMENDATIONS 1) The Government of the Virgin Islands should pass legislation prohibiting the importation and sale of toilets which use more than 3.6 gallons of water per flush after January 1, 1980. 2) The Government of the Virgin Islands should immediately embark on an investment program to replace existing conventional toilet fixtures in public housing, public schools, and government offices with low-flush toilets. 3) The Government of the Virgin Islands should develop and implement a public relations campaign which would stress the cost effectiveness of conserving water for private individuals and commercial enterprises in the Territory, and should encourage the use of water saving devices such as low-flush toilets. 4) The Government of the Virgin Islands should study the cost effectiveness of offering tax incentives to private individuals and commercial enterprises for retrofitting existing plumbing fixtures with water saving equipment, especially low-flush toilets. ACKNOWLEDGEMENTS The daily efforts of Margaret Blyden at Red Hook are sincerely appreciated The advice of Leonard Brown was invaluable The assistance and concern of Frank Kay is gratefully acknowledged. Literature Buros, O.K. 1976. A Water management plan for St. Croix, USVI. Black, Crow, and Eidsness, Inc., Gainsville, Florida. Lackey, A.M. Economic inventory of the supply and use of water for rural domestic purposes. USDA, Natural Resource Economics Division, Washington, D.C. Massachusetts EOEA. 1978. Massachusetts water supply policy statement,. Executive Office of Environmental Affairs, Boston, Massachusetts. Milne, M. 1976. Residential water conservation. California Water Resources Center, University of California,. Davis, California. V.1. Housing Authority. 1978. Report on the current water crisis. V.1. Housing Authority, St. Thomas, United States Virgin Islands. V.1. Planning Office. 1977. Land USe and housing elements. Virgin Islands Planning Office, St. Thomas, United States Virgin Islands. Table 1 Water Center Water Meter Records PROJECT NO. A-004-VI The Water Economy of a Low—flush Toilet ______________________________________________________ Quarterly Date Meter Gallons No. Flushes Gal/Day For Analysis 2/24/77 250.8 /25 270.6 19.8 39 19.8 /26 329.9 59.3 118 59.3 /27 359.7 29.8 59 29.8 /28 419.2 59.5 119 59.5 3/1 443.3 24.1 48 24.1 /2 471.8 28.5 57 28.5 /3 526.7 54.9 109 54.9 /4 560.4 33.7 67 33.7 /5 601.3 40.9 • 81 40.9 /6 631.9 30.6 61 30.6 /7 673.0 41.1 82 41.1 /8 708.5 35.5 71 35.5 /9 734.9 26.4 52 26.4 /10 /17 /22 /24 790.0 1052.7 1283.5 1390.2 .55.1 262.7 230.8 106.7 110 535 461 213 55.1 375* 52.5* 534* Analysis Incomplete 4/13 5/9 5/16 6/1 6/13 2123 2725 2965 3461 3746 733 602 239 496 285 1466 1204 478 992 570 36.7* 23.2* 34.2* 31.0* 23.8* First 2355 gallons 7/13 8/15 8/25 9/26 4707 5600 5904 6742 961 893 304 838 1922 1786 608 1676 32.0 * 27.1 * 30.4 * 26.2 * Second 2996 gallons 10/17 12/15 7258 9944 516 2686 1032 5372 16.6* 45.5 * Third 3202 gallons 1/13/78 3/1 4/13 10856 12620 13961 912 1764 1341 1824 3528 2682 37.5* 31.2* Fourth 4017 gallons 6/22/78 16050 2089 4178 29.8* Incomplete 15789.4 gal 32. 7*gal /day * = Average Reporting Quarter Department of Public Works Water Center Records First 1976 Second 1976 Third 1976 Fourth 1976 First 1977 15,000 gallons 15,000 18,000 7,500 10,000 1,140* gallons Second 1977 Third 1977 Fourth 1977 First 1978 3,000 3,000 4,000 4,000 2,355 2,996 3,202 4,017 Second 1978 7,000 2,089* Third 1978 2,000 Fourth 1978 2,000 First 1979 2,000 Second 1979 2,000 Analysis * = Incomplete Record WRRC/ap/79 Table 3 Installing Costs of Low Flush Toilets at Red Hook, St.Thomas PROJECT NO A-004 VI The Water Econonmy of a Low-Fluh Toilet __________________________________________________________________ 5 Microphor toilets (LF-310) @ $385 $1925 1 Compressor (30gal) 485 l Water meter 70 P1umbng Materials 100 Sub—total (equipmentt & materials) 2580 Installation 1000 Total Cost for Installation $3580 Table 4 Water Distributed From The Government Standpipe To Red Hook From January 1976 To December 1976. 1976 January 5,750 gals 23 tons February 3,500 14 March 5,750 23 April 5,000 20 May 5,000 20 June 5,000 20 Ju1y 6,000 24 August 5,000 20 September 7,000 28 October 4,000 16 November 500 2 December 3,000 12 ___________ _________ 55,500gals 222 Tons Table 5 Water Distributed Prom The Government Standpipe To Red Hook From January 3.977 To December 1977. 1977 January 4,500 gals 18 tons February 3,000 12 March 2,500 10 April 1,000 4 May 1,000 4 June 1,000 4 Ju1y 1,000 4 August 1,000 4 September 1,000 4 October 1,000 4 November 1,000 4 December 2,000 8 ___________ _________ 20,000gals 80 Tons Table 6 Water Distributed From The Government Standpipe To Red Rook From January 1978 To September 1978 1978 January 1,000 gals 23 tons February 2,000 14 March 1,000 23 April 2,000 20 May 3,000 20 June 2,000 20 Ju1y None 24 August 1,000 20 September 1,000 28 ___________ _________ 13,500gals 52 Tons Table 7 Water Distributed From The Government Standpipe To Red hook From October 1978 To May 1979. 1978 October 1,000 16 November 1,000 2 December None None 1979 January 1,000 4 February 1,000 4 March None None April 2,000 8 May None None ___________ _________ 6,000gals 24 Tons