Drinking Water Affordability Act This bill amends the Safe Drinking Water Act to revise requirements concerning national primary drinking water regulations, including by: removing a requirement that the Environmental Protection Agency (EPA) maintain, or provide greater, protection of human health when revising those regulations; extending the repayment schedule for loans from the drinking water state revolving funds (SRFs); authorizing states to protect public drinking water source areas; removing federal reporting requirements if state or local requirements are not less stringent than federal requirements; and requiring the EPA to conduct a review on best practices for streamlining the application process for public water systems to receive loans or loan guarantees from an SRF as well as best practices for administering SRFs efficiently.