The problem of lead content in U.S. drinking water extends beyond Flint. For examples:
LAUSD and Los Angeles, CA see http://achieve.lausd.net/Page/3450 and http://achieve.lausd.net/cms/lib08/CA01000043/Centricity/domain/135/pdf%20files/LeadAdvisory.pdf (This testing would tend to imply that all LADWP customers should have the same concerns.)
Washington, DC see http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5312a6.htm
Sebring, OH see http://www.planetizen.com/node/83433/excessive-lead-drinking-water-spread-ohio
My guess is that this problem impacts almost every public utility in the United States (and the world, for that matter) with infrastructure more than 30 years old.
Remember that “plumber” is from the Latin plumbarius (lead worker). Originally, all pipes were lead. Lead solder wasn’t banned in the U.S. until June 1986 (Safe Drinking Water Act).
A major part of the problem may also involve the testing protocols. See, for example, http://www.theguardian.com/environment/2016/mar/06/water-utilities-lead-testing-analysis-us-cities?utm_source=esp&utm_medium=Email&utm_campaign=GU+Today+USA+-+Version+CB+header&utm_term=160425&subid=8198027&CMP=ema_565