Plumbing supplies such as bathroom fixtures, faucets, drains, pipe, fittings, and plumbing hardware are used to build and maintain plumbing systems. Ball valves, check valves, and other plumbing valves are used for controlling flow, pressure, and temperature in commercial, residential, and industrial plumbing systems. Filters, strainers, and other filtration equipment remove unwanted chemicals and contaminants from a water supply. Electric or gas water heaters provide hot water for buildings.