The number of years that most U.S. cities have to replace lead water pipes under strict new rules proposed by the Environmental Protection Agency. The proposal would require utilities to replace lead pipes even if their lead levels aren’t too high and they would lower the level of lead at which utilities are forced to take action. Most cities have not been required to replace their lead pipes and many don’t even know where they are; if a city has a lot of lead pipes, it may be given a longer deadline.