Virtual Lavatory  
Lifting the lid: The Ballcock
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The ballcock, also known as a ball valve, float valve or float activated valve unit, comes in many forms. All consist of a large float, usually made of plastic, attached to a valve via a long lever. The most common form is shown below.

Figure 1 shows a detailed cross section of the ballcock's valve. Water enters through the nozzle (A) into the barrel (B) which contains a plunger (C) with a rubber washer (D). The lever arm (E) is connected to the float at one end and fixed to the pivot (F). The other end of the lever extends through a slot into the barrel and into a groove (G) in the plunger. As the water in the cistern drops the float falls, the lever rotates anticlockwise about the pivot, pulling the plunger away from the inlet nozzle, letting water in. As the float rises once the cistern has stopped flushing, the lever is rotated clockwise, and the plunger forced against the nozzle by pressure from the lever. This enables the cistern to be refilled to the same level after each flush.

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