Affordable Safe Drinking Water Act of 2020 This bill revises the clean water state revolving fund (SRF) program and the drinking water SRF program. Both programs provide financial assistance for water infrastructure. The bill removes the 30-year term limits for loans under the SRF programs. Thus, new loans under the programs may have terms up to the projected useful life of the projects. Loan terms for existing loans may, on agreement of the parties to the loan, be extended. In addition, the bill allows states to use a percentage of SRF funds to replace pipes, plumbing fittings, and fixtures that carry water contaminated with lead or perfluoroalkyl or polyfluoroalkyl substances (commonly referred to as PFAS) at certain state, municipal, or tribal facilities (e.g., schools, parks, and senior centers) that provide the public or employees with drinking water. PFAS are man-made and may have adverse human health effects.