Stopcock

A stopcock is a form of ball valve used to control the flow of a liquid or gas. Compared to the progressive control of a gate valve a stop cock's is coarse, confining their use principally to on-off applications.

Use

Water service

Stopcocks are used to grossly regulate the flow of tap water in residential and commercial services. One is found at the junction of a water main and the branch leading to an individual service (allowing the service to be isolated from the main trunk), a second inside the structure (allowing its plumbing to be isolated from the branch line leading into it). Either is employed when maintenance or emergency repairs are conducted.

Laboratory

For laboratory glassware, items sometimes have plug valves with conically-tapered inserts called stopcocks (sometimes referred to as "plugs" by laypeople) with different bores. The valve bodies are usually made of glass, while the plugs are made of glass or Teflon. You also can find valves with Teflon spindle (for example one way valves or angled valves) When the plug is made of glass, the handle and plug are fused together in one piece out of glass. When both valve body and plug are made of glass, grease is usually used to give a good seal, as well as to prevent the valve from seizing and subsequently cracking.