The mechanism inside a gravity-flush toilet tank that refills the water after a flush. It consists of a supply valve controlled by a floating ball or cup on a lever arm. As the water level drops, the float lowers and opens the valve to let fresh water in, shutting it off once the tank reaches the correct capacity.
Heard on the job
The tank keeps running because the ballcock is scaled up and won't seat properly.
Insider tip
While the traditional brass rod and hollow copper ball design gives this part its name, plastic cup-style fill valves serve the exact same function and are still widely called ballcocks by tradespeople.
Also heard as
- fill valve
- float valve