The 2013 revised total coliform rule and the 1989 total coliform rule are the only microbial drinking water regulations that apply to all public water systems. The revised rule highlights the frequency and timing of microbial testing by water systems based on population served, system type, and source water type. It also places a legal limit on the level for Escherichia coli. Potential health threats must be disclosed to EPA or the appropriate state agency, and public notification is required in some circumstances.
