Manda Metzger, a project manager with PWSA, holds a removed lead service line. (Photo by Ryan Loew/PublicSource)

Pittsburgh’s water authority estimates that 25% of service lines contain lead. But is their math right?

Block by block, home after home, a crew of three contractors walks slowly, stopping every few feet to plant a small pink flag into the ground. The flags mark the lids to curb boxes, which provide underground access to the service lines carrying water to each home. Since January, when curb box inspections began in earnest, the crew has been seeking the answer to a simple, yet critical question: How many lead service lines are there in Pittsburgh? Though the lead test results released Tuesday by the Pittsburgh Water and Sewer Authority do not exceed the federal action limit, the question must still be answered. For one, the 90th-percentile result of 15 ppb is the threshold.