What function does a faucet serve in a plumbing system?

A faucet functions primarily to control the flow of water from a water supply system. It allows users to easily manage the rate at which water is dispensed, making it possible to turn the water on or off and adjust the temperature by mixing hot and cold water. This control is crucial for everyday tasks such as washing hands, cooking, and cleaning.

Faucets are designed specifically for this purpose, featuring different mechanisms (like compression, cartridge, and ball type) that enable precise handling of water flow. Unlike other components mentioned, a faucet is not involved in regulating pressure within a drainage system, trapping odors, or providing access to drainage lines, which are the functions of different plumbing components such as traps or cleanouts. This clarity about a faucet's role highlights its essential function in facilitating the usage of water in residential and commercial settings.