ball cock

or ball·cock

noun

a device for regulating the supply of water in a tank, cistern, or the like, consisting essentially of a valve connected to a hollow floating ball which by its rise or fall shuts or opens the valve.

Origin of ball cock

First recorded in 1780–90

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for ball cock

Historical Examples of ball cock

And Oswald could not prevent his fiddling with the pipes and the ball-cock a little.
New Treasure Seekers
E. (Edith) Nesbit
It should have a large evaporating vessel, with a ball-cock to supply it.
Lectures on Ventilation
Lewis W. Leeds
In the larger sizes the tank is automatically refilled from a water service through a ball-cock.
Acetylene, The Principles Of Its Generation And Use
F. H. Leeds
This cistern is fitted with a ball-cock, by which arrangement the liquid can be drawn off by a system of wooden pipes as required.
Cooley's Practical Receipts, Volume II
Arnold Cooley
A tank situated in the roof, and fed from the main by a ball-cock valve, communicates with A through the siphon pipe S.
How it Works
Archibald Williams

British Dictionary definitions for ball cock

ball cock

noun

a device for regulating the flow of a liquid into a tank, cistern, etc, consisting of a floating ball mounted at one end of an arm and a valve on the other end that opens and closes as the ball falls and rises with the water level in the cistern

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012