Seawater flushing

A flush toilet is a toilet that disposes of human excreta (urine and feces) by using water to flush it through a drainpipe to another location for disposal, thus maintaining a separation between humans and their excreta. Flush toilets can be designed for sitting (in which case they are also called "Western" toilets) or for squatting, in the case of squat toilets. The opposite of a flush toilet is a dry toilet, which uses no water for flushing.

Flush toilets usually incorporate an "S", "U", "J", or "P" shaped bend (called a trap, such as P trap or S trap) that causes the water in the toilet bowl to collect and act as a seal against sewer gases (trapping the gases). Since flush toilets are typically not designed to handle waste on site, their drain pipes must be connected to waste conveyance and waste treatment systems. When a toilet is flushed, the wastewater flows into a septic tank or sewage system and from there to a sewage treatment plant.

A flush toilet may be colloquially called a lavatory, water closet (abbreviated W.C.), loo, comfort room (abbreviated C.R.), and many other names.

A flush toilet is different from a urinal, which is designed to handle only liquid waste; or from a bidet, which can be used for personal cleansing after toilet use.

A typical flush toilet is a vitreous, ceramic bowl containing water, plus plumbing to rapidly fill it with more water. The water in the toilet bowl is connected to a hollow drain pipe shaped like an upside-down U connecting the drain. One side of the U channel is arranged as a hollow siphon tube longer than the water in the bowl is high. The siphon tube connects to the drain. The top of the upside-down U-shaped drain pipe limits the height of the water in the bowl before it flows down the drain. If water is poured slowly into the bowl it simply flows over the rim of the upside-down U and pours slowly down the drain — thus the toilet does not flush. The standing water in the bowl acts as a barrier to sewer gas coming out of the sewer through the drain, and also as a receptacle for waste. Sewer gas is vented through a separate vent pipe attached to the sewer line.

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