DWU has contractual relations with 31 wholesale water and wastewater customers. There are five general types of relationships:   Wholesale customers to DWU include the communities of Addison, Carrollton, Cedar Hill, Cockrell Hill, The Colony, Coppell, Denton, DeSoto, Duncanville, Farmers Branch, Flower Mound, Glenn Heights, Grand Prairie, Grapevine, Highland Park, Hutchings, Irving, Lancaster, Lewisville, Mesquite, Ovilla, Red Oak, Richardson, Seagoville, University Park, and Wilmer, as well as Dallas County WCID #6, Dallas/Fort Worth International Airport, Ellis County WCID #1, and the Upper Trinity Regional Water District. Since the early 1980s City of Dallas Water Utilities has had conservation programs. Over the years activities have increased to include children activities, Water-Wise landscape seminars, an annual Water-Wise Landscape tour and more. In 2001, the Dallas City Council took conservation efforts to another level by adopting an irrigation ordinance which included time-of-day watering restrictions. In April 2012, the Council voted to adopt maximum twice-weekly watering, which allows outdoor irrigation only twice per week according to a schedule based on even/odd street address numbers. The ordinance and other measures have reduced gallons per capita per day in Dallas by 26% since 2001 resulting in:    DWU has over 300,000 meters in its system. Approximately 6800 are AMI Fixed network units. Meters range in size from 5/8" to 10" or larger. The water distribution system of Dallas Water Utilities (DWU) is one of the largest in the United States. As of June 2003, DWU provided retail water service to just over 1.2 million people within the Dallas city limits. The major distribution system facilities include 28 pump stations (including the high service pump stations at the three water treatment plants), 11 ground storage reservoirs, 9 elevated tanks, and 78 vault structures separate from the major facilities, in addition to over of distribution and transmission main. The distribution system is divided into 17 pressure zones to maintain adequate water pressures throughout the system. There are four major pressure zones (Central Low, North High, East High, and South High), and five smaller secondary pressure zones (Meandering Way High, Red Bird High, Trinity Heights, Pleasant Grove, and Cedardale) which comprise most of the Dallas service area. Each of the nine major and secondary pressure zones are supplied by one or more pump stations and have elevated or ground storage facilities that establish the static hydraulic gradient for each zone.