What are fixtures in plumbing?

In plumbing, fixtures are the devices and appliances that receive water from the supply system and discharge it into the drainage system, serving as the fixed access points for a building's water use. The standard plumbing fixtures include toilets (water closets), lavatories and washbasins, bathtubs, showers, bidets, kitchen sinks, utility or laundry sinks, faucets and taps, and, in many classifications, plumbed appliances such as dishwashers, garbage disposals, and water heaters. Each fixture is defined by its permanent connections: a water supply line (often with a shut-off valve), a fixture trap (the P-trap or S-trap) that holds a water seal to block sewer gases, and a drain line connected to the building's soil stack or sewer system. Plumbing codes treat fixtures as the fundamental units of system design: each fixture is assigned a "fixture unit" value, and the total fixture-unit load determines the required sizes of water supply pipes, drain lines, and vents. Codes also dictate minimum fixture counts for dwellings and for public and commercial buildings based on occupancy. Fixtures are typically made from vitreous china, porcelain enamel, stainless steel, acrylic, or enameled cast iron for durability in wet conditions, and modern standards increasingly require water-efficient fixtures such as low-flow toilets and aerated faucets. In property law, plumbing fixtures are legally part of the real estate and transfer to the buyer upon sale, which is why toilets, tubs, and sinks are among the clearest examples of fixtures in real estate transactions.