A kitchen's plumbing system consists of water-supply lines and, in many cases, a gas-supply pipe. The visible part of the sink's plumbing is nearly always located directly below the sink, inside the sink's base cabinet. Generally, a flexible gas connector, controlled by a gas valve located at the wall or floor beneath a gas range, serve that appliance

On the faucet side of the cold-water shutoff valve, there may be other water connections, too--sometimes by way of a saddle valve. This is where connections are made with flexible copper or plastic tubing to serve a water-treatment, instant-hot water dispenser, and the like.

Flexible supply tubes connect the valves to the threaded tailpieces of the faucet. Faucets with a separate or integral sprayer have a hose that connects onto another tailpiece at the center of the faucet body.