Sewer gas in the context of "Trap (plumbing)"

A flush toilet (also known as a flushing toilet, water closet (WC); see also toilet names) is a toilet that disposes of human waste (i.e., urine and feces) by collecting it in a bowl and then using the force of water to channel it ("flush" it) through a drainpipe to another location for treatment, either nearby or at a communal facility. Flush toilets can be designed for sitting or squatting (often regionally differentiated). Most modern sewage treatment systems are also designed to process specially designed toilet paper, and there is increasing interest for flushable wet wipes. Porcelain (sometimes with vitreous china) is a popular material for these toilets, although public or institutional ones may be made of metal or other materials.

Flush toilets are a type of plumbing fixture, and usually incorporate a bend called a trap (S-, U-, J-, or P-shaped) that causes water to collect in the toilet bowl – to hold the waste and act as a seal against noxious sewer gases. Urban and suburban flush toilets are connected to a sewerage system that conveys wastewater to a sewage treatment plant; rurally, a septic tank or composting system is mostly used.