The DC Water and Sewer Authority (WASA) distributes water to residences and businesses throughout the District for drinking, fire fighting and other uses. WASA purchases the drinking water from the US Army Corps of Engineers Washington Aqueduct. The Washington Aqueduct (WA) withdraws approximately 180 million gallons of water each day from the Potomac River at the Great Falls and the Little Falls intakes and then treats the water at the two water treatment plants, Dalecarlia and McMillan. The key treatment processes at the WA Dalecarlia and McMillan facilities include sedimentation, filtration, fluoridation, pH adjustment, primary disinfection using free chlorine, secondary disinfection with chloramines through the addition of ammonia to convert the chlorine to choloramine, and finally corrosion control with orthophosphate. This orthophosphate treatment process began system-wide in August 2004 to help reduce the tendency of water to corrode certain metals. Compliance water sample analysis through the end of 2004 indicated that the addition of orthophosphate has significantly reduced the corrosive effects of water on service line pipes and other plumbing fixtures that may contain lead.