Water Efficiency, Conservation, and Sustainability Act of 2023 This bill establishes three grant programs within the Environmental Protection Agency (EPA) to address water efficiency and water losses. First, the EPA must establish a grant program to assist states, local governments, tribal governments, public water systems, and nonprofit organizations in carrying out their water efficiency incentive programs. Second, the EPA must establish and carry out a program that provides grants and technical assistance for conducting annual audits of public water systems, implementing controls to address losses identified in the audits, and helping public water systems that have conducted and validated audits to establish water loss control programs. Third, the EPA must establish a grant program to assist states, tribal governments, and local governments in adopting and implementing certain water-efficient plumbing codes.