A toilet syphonic system uses water displacement to create a vacuum that sucks the contents of the toilet bowl down into the waste pipe. Toilets equipped with a syphonic system have a rubber diaphragm connected to the flushing handle. Pressing the handle lifts the diaphragm, moving a quantity of water from the tank into the bowl. The influx of water pushes the bowl's contents into the waste pipe.
Syphonic toilets are the most prevalent type of toilet in the United States. The other style, called a wash-down toilet, is more popular in Europe. When a wash-down toilet flushes, water from the toilet tank enters the bowl and displaces the waste material therein, forcing it down into the waste pipe. Wash-down toilets do not employ the sucking action that characterizes syphonic toilets.
There are several other toilet styles. According to Greywater Action, one of the most unusual is the dry composting toilet. These toilets use beneficial bacteria to break down human waste. Some composting toilets involve small amounts of flushing water, while others use none at all. This type of toilet provides convenient waste disposal in areas where water is scarce. They are often installed in parks and rural rest stop areas. Composting toilets are particularly popular in the United Kingdom, Sweden and the United States.