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How Does a Flush Toilet Work

How Does a Flush Toilet WorkHave you ever wondered how the flush system of a toilet works? The flush mechanism is based on the principles of gravity and uses a simple system of water pressure, levers, siphons, valves and suction. Toilets are constructed of two main components: a toilet tank or cistern at the back and the toilet bowl or basin at the bottom which is covered by the seat. All of the important parts of the flush mechanism are hidden in the toilet tank which can be accessed by simply lifting up the ceramic lid. A standard toilet tank will contain several crucial components including: a float ball, a float rod, inlet valve, inlet tube, handle, piston and a siphon.

The toilet tank is filled with clean water through an inlet tube which is supplied and controlled by the inlet valve. Typical toilet tanks contain a float ball which is attached to a float rod. The ball is designed to float on the surface of the water. As the ball rises, the connected rod closes the inlet valve to turn off the water supply. When the toilet tank is full, the rod presses hard enough against the inlet valve to control the release of water from the inlet tube in order to prevent the tank overflowing.

U Shaped Siphon

How Does a Flush Toilet WorkWhen the toilet handle is pressed, a lever inside the toilet tank pulls up a plastic piston at the base of the cistern. This action creates suction in a U shaped siphon which forces water from the toilet tank to rush past the piston, through the siphon and into the toilet bowl. When the handle is released, the piston drops back into its original position ready for the handle to be pressed again. The suction mechanism empties the toilet tank fairly rapidly and causes the float ball to fall to the bottom of the tank. This means that the float rod releases the inlet valve and the toilet tank will be filled up again with fresh water from the inlet tube.

S Shaped Pipe

The clean water released through the suction action of the siphon is flushed from the toilet tank into the bowl. The rush of water will clean the sides of the toilet bowl and under the rim where it is difficult to access. The force of gravity pushes the excess liquid and any waste carried with it out through a bend in a short S shaped pipe which connects to the drain. Water flushed through the pipe will carry all waste with it which is then taken to a treatment plant or septic tank. Excess clean water released from the toilet tank will remain at the bottom of the toilet bowl ready for the next use. The S shaped bend in the sewage pipe traps bad odors from the drain pipe and sewage system. The S pipe also causes another suction action which assists in speeding up the flushing process.