What is a drain cock?
A drain cock (also called a drain valve or drain-off valve) is a valve that allows water or another fluid to be drained from a pipe, radiator or heating system. The valve is fitted at the lowest point of the system so that the liquid can flow out by gravity.
How does a drain cock work?
A drain cock is a simple ball valve or screw-down valve that is normally closed. During maintenance or repairs it is opened to empty the system. A hose is connected to catch or direct the water.
Types
- Ball valve — quick operation with a quarter turn
- Screw-down valve — opened and closed by turning
- Hose-union drain cock — has a connection for a garden hose
- Combined air vent and drain — combines venting and draining in one fitting
Applications
- Central heating — drain cock at the boiler or at the lowest point to fill or empty the system
- Radiators — each radiator has a drain point for disconnection
- Water supply — outside taps are drained down in winter to prevent frost damage
- Solar thermal — drain cock to empty the system during maintenance
- Swimming pool pipework — for winterising the plumbing
Related terms
- Boiler
- Radiator
- Pipework
- Air vent
- Water supply
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