上海的旧式里弄和2000年前建成的住宅小区,地下供水管多为易被腐蚀的镀锌铁管,屋顶水箱内壁也布满锈垢,从而形成二次供水污染。从2007年开始,上海已对中心城区8100个小区居民住宅的二次供水设施进行统一改造,2009年基本完成,并逐步实现供水企业“管水到表”。届时,住宅区龙头水的水质应与出厂水水质基本保持同一水平。 Shanghai's old neighborhoods and residential areas built 2000 years ago, mostly underground corrosion of galvanized steel pipe, roof tank wall is also covered with scale, resulting in secondary water pollution. Since 2007, Shanghai has unifiedly rebuilt the secondary water supply facilities of residential buildings in 8100 residential districts in the downtown area and basically completed in 2009, and gradually realized the water supply management. By then, the water quality of the leading residential water should be the same as that of the factory water quality.