IOWA CITY, IOWA — A federal rule that took effect in 1991 is designed to protect the public from unsafe levels of lead in drinking water. Some answers to common questions about how it works:

Q: How often do water systems have to test for lead?

A: Systems must test every six months until they have achieved compliance and can qualify for a reduced sampling program. Systems that serve more than 50,000 customers can test annually as soon as two consecutive testing periods are below the level that requires federal action. Smaller systems that meet that standard can test every three years.

Q: How do cities decide which homes to test and how are samples collected?

A: Water systems are supposed to collect samples from buildings that are at highest risk of lead contamination. Homeowners are recruited to voluntarily collect the samples, which must be drawn from a tap that has not been used for at least six hours.

Q: How many samples are collected?

A: It depends on a system's size and whether it is on a reduced-sampling program. The number can vary from 100 samples for the largest water districts to five for the smallest.

Q: What is the threshold for the EPA considering a water system in violation?

A: A system is considered out of compliance if more than 10 percent of the sites sampled have lead levels above the federal-action level of 15 parts per billion.


Q: What happens then?

A: Within 60 days, the system must notify customers about the test results, inform them of the possible health risks and outline steps they can take to protect themselves. Those suggestions often include running water for 30 seconds to flush lead, using cold water for cooking and making baby formula, and replacing lead-based plumbing fixtures and service lines. Buying water filters and bottled water also are options.

Q: Are the water systems required to do anything else?

A: Yes. Typically, they are required to study and eventually add corrosion-control treatments to the water supply. Often, systems use a chemical such as phosphate to make the water less corrosive and therefore less likely to leach lead from service lines and plumbing fixtures. They may also be required to replace some lead service lines, which connect water mains to individual homes.

Q: Do all schools and day care centers have to test for lead?

A: No. In fact, most schools are not required to do testing under the rule. Only schools and day care centers that operate their own water systems are required to test for lead. Public and private schools and day care facilities that rely on a municipal water system are not required to test, although some do in the interest of safety.

Q: How do I know if my house might have lead in the water?

A: Just because your community is over or under the federal limit does not mean the drinking water at your house is safe or unsafe. The best way to know might be to call your water supplier to have it tested for lead, a service that many are now offering for free.

Q: Why don't more water systems replace their old lead pipes?

A: The cost, along with some questions about ownership. Many water systems have replaced or are in the process of replacing all of the lead-based water lines they own. But millions of miles of service lines deliver water to old homes, schools and businesses, and often cost $2,000 to $3,000 per location to replace. Property owners are generally responsible for those pipes.