To construct and maintain plumbing systems, plumbing supplies such as bathroom fixtures, faucets, drains, tubing, fittings, and plumbing hardware are needed. In commercial, residential, and industrial plumbing systems, ball valves, check valves, and other plumbing valves are used to manage flow, pressure, and temperature. Unwanted chemicals and impurities are removed from a water supply using filters, strainers, and other filtration devices. Buildings require hot water, which is provided by electric or gas water heaters.