A toilet plunger, sometimes also known as a "
plumber's helper", or more simply,
plunger, is a simple device for clearing blockages in a
toilet's drain which prevent the toilet bowl from properly emptying after flushing.
The most common toilet plunger design consists of a semiflexible rubber bell known as a force cup attached to a long, firm shaft serving as a handle (see fig 1). To use, the force cup is placed around the toilet bowl's drain so as to create a tight seal. The user then presses down on the handle, which causes the rubber of the force cup to bend inwards (fig 2).
/\
| |
| |
| |
| |
| | /\
| | | |
| | <-- Handle --> | |
| | | |
| | | |
| | | |
----+--+---- | |
/ \ | |
/ \ | |
/ \ <-- Force /\ | | /\
| | cup --> | \ | | / |
| | | ----+--+---- |
Figure 1 Figure 2
As you can see, this decreases the volume of the force cup, thus increasing the pressure of its contents. As water is effectively incompressible, this pressure is transmitted to the blockage. When the handle is pulled back, the resultant suction acts on the blockage in the opposite direction. Hopefully, this force will break up and dislodge the blockage; if not, the procedure ("plunging") is repeated until satisfactory results are attained.
As the principle on which these plungers operate is not specific to toilets, they may also be used to clear other soft blockages like hairballs in sink or shower drains. More advanced forms exist, employing more complex design or compressed CO2, but given a force cup of sufficient volume, the basic design should be adequate for common household use.