The mandate of a Philippine Municipal Water System Office, established under Presidential Decree 198 (PD 198), is to provide efficient, adequate, reliable, and affordable potable water to communities by operating, maintaining, and developing water supply systems, including acquiring sources, building infrastructure, managing distribution, and ensuring water quality, with the goal of improving local quality of life while safeguarding resources. They also often handle wastewater services and promote water conservation, acting as local partners for LGUs.