(CNN) The Environmental Protection Agency is proposing its first major revision in two decades of federal regulations on lead in drinking water, after scandals in Flint, Michigan, and other cities, eroded public confidence that tap water is safe to drink.

The proposed lead and copper rule would change the requirements that local water systems must meet for testing and, if lead content is above allowable levels, the procedures to replace lead service lines from their networks.

The rules would not change the 15 parts-per-billion limit on lead in water. By comparison, Canada has a threshold of 5 parts per billion.

They would, however, require water authorities to begin developing plans when they are at risk of reaching that threshold, and to notify customers within 24 hours of noncompliant test results. They would also prohibit practices, such as flushing pipes prior to testing, that water systems have used to get around the rules.

EPA Administrator Andrew Wheeler said Thursday that the new rules "would require water systems to act sooner," would "better protect children" and would ban ways that water systems effectively rigged their lead content numbers.

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