Amends the PFAS Reduction Act. Provides that, on or before December 31, 2025, the owner or operator of each community water system, community wastewater system, and nontransient, noncommunity water system shall conduct monitoring for perfluoroalkyl and polyfluoroalkyl substances (PFAS), using standard laboratory methods established by the United States Environmental Protection Agency in effect at the time of sampling, and shall conduct additional monitoring for the presence of PFAS contaminants under specified circumstances. Provides that, if monitoring results confirm the presence of any PFAS contaminants, individually or in combination in excess of 20 nanograms per liter, then the Illinois Environmental Protection Agency shall direct the owner or operator of the community water system, community wastewater system, or nontransient, noncommunity water system to issue a notice to all users of the system to inform them of the detected PFAS concentration and potential risk to public health until the level is below 20 nanograms per liter. Sets forth civil penalties for violation of the provisions. Grants rulemaking powers to the Illinois Pollution Control Board. Defines terms.