Drinking Water Infrastructure Act of 2020 This bill addresses drinking water infrastructure, including by revising and reauthorizing programs regarding tribal water systems and emergency situations affecting public water systems, expanding the allowable uses of certain grants to include remediation of groundwater contamination, expanding the allowable uses of assistance for public water systems serving small and disadvantaged communities, and establishing a pilot program utilizing mapping to reduce lead in drinking water. The bill also requires the Environmental Protection Agency to establish a national primary drinking water regulation for perfluoroalkyl and polyfluoroalkyl substances, commonly referred to as PFAS. These substances are man-made and may have adverse human health effects. A variety of products contain the compounds, such as nonstick cookware or weatherproof clothing.