Sustainable Building Technical Manual - Etn-presco.net

Water Efficiency and Conservation★ S I G N I F I CA N C E .The amount of water available for use on the planet is finite, so as population grows, theavailable supply of water per person drops. Per capita water supplies worldwide havedecreased by one-third since 1970, as the world’s population has grown by 1.8 billion.Since 1980, global water use has more than tripled and is currently estimated at 4,340cubic kilometers per year. Demand in every area of water use—urban, industrial, andagricultural—has increased, often because of mismanagement, overuse, and waste. 8 Manyparts of the world are now experiencing rising water costs, seasonal shortages, andunpredictable quality and availability of supplies.As water demands increase and municipalities must fund new water supply and treatmentfacilities, costs are passed on to the consumer. Many cities are using conservationrate structures in which larger users pay higher rates. Higher water use also adds to maintenanceand life-cycle costs of facility operation. Efficiency and conservation in institutional,commercial, and industrial water use can result in impressive savings of bothwater and money—not just in water-use fees but also in sewage treatment costs, energyuse, chemical use, and capacity charges and limits.. ☛ SUGGESTED PRACTICES AND CHECKLISTIWater Harvesting❑ Collect and use “harvested” water.Water harvesting means collecting runoff from the soil’s surface, paved surfaces, andother sources, and storing it for future use such as irrigation. Harvested water caninclude stormwater and irrigation runoff, water from cooling towers and heating, ventilating,and air-conditioning (HVAC) systems, and water from swales and otherdrainage structures directed into collection areas. After collection in a storage tank orpond, harvested runoff must be pressurized in order to be used in an irrigation system.– Utilize gravity flow to collect runoff into harvesting areas such as storage tanks, openponds, or detention basins.– Direct rainfall from roofs and water from cooling towers into runoff harvesting areas.Rainwater Harvesting❑ Collect and use rainwater.Collecting and using precipitation from a roof or other catchment area is an excellentway to take advantage of natural site resources, to reduce site runoff and the need forrunoff-control devices, and to minimize the need for utility-provided water. Rainwatercollection has long been utilized in arid parts of the world. Particularly in areas wherepopulations are dispersed, rainwater collection offers a low-cost alternative to centralizedpiped water supply. In moist climate zones, rainwater collection is an excellentsupplemental source of water. 9❑ Consider quality of rainwater.Areas with extremely poor air quality may yield rainfall of poor quality. Rainfall insome areas is highly acidic, and therefore, undesirable for reuse. If the collection areahas many overhanging tree branches, the collected rainwater will contain more debrisand may appear brownish in color (caused by tannic acids drawn from plant debris).In areas with hard water, rainwater is preferable for its softness, cleaning abilities, andability to extend the life of appliances such as water heaters and coffeemakers. The useand collection of rainwater is not federally regulated, and guidelines pertaining to its