Random Tests Last Summer Found High Levels in 4,000 Homes Throughout City Tap water in thousands of District houses has recently tested above the federal limit for lead contamination, a new phenomenon that has baffled the D.C. Water and Sewer Authority and forced the agency to begin replacing service pipes. Two-thirds of the 6,118 residences that WASA tested last summer, or 4,075 homes, had water that exceeded the lead limit of 15 parts per billion set by the Environmental Protection Agency in 1991. This is the first time the city's water has shown significant lead contamination since the late 1980s,...