Sillcock

A sillcock is a threaded faucet assembly designed to attach to a water supply line inside a building, pass through the exterior wall, and terminate outside for garden hose or outdoor water access. The shank—the cylindrical part between the interior nut and the exterior valve body—is long enough to span wall thickness plus any insulation or siding without exposing pipe threads to weather.

In the field, you'll install the female threaded inlet inside, screw it onto supply tubing, and tighten a packing nut and washer against the interior wall surface to create a seal. The exterior valve handle and outlet stay exposed to freeze cycles and UV. Most codes require either a frost-proof sillcock with an internal shutoff and drain, or a shutoff valve and drain valve installed on the supply line inside so you can winterize the line. Standard sillcocks come in quarter-turn (ball) or compression-type handles.

Frost-proof models—also called freeze-proof—have the shutoff seat positioned 6 to 12 inches inside the wall so water drains out of the external part when you close the handle, preventing burst damage in cold climates. Non-frost models leave water in the exterior body and need manual drain valves to avoid freeze damage. Always pitch the supply line slightly toward the interior shutoff for complete drainage.