Flexible siphons are curved or specially shaped parts of a pipe, duct or sanitary appliance which has a section always submerged in water, be it a sink, bath, wash basin or toilet. It generally takes the form of a distorted letter L or a letter U.
It has three basic parts, the inlet and outlet sections where water enters or exits and consists of a siphon tube. The water runs freelyinto the siphon upon gravity and goes into another stream, the so-called pressure flow. This siphon pipe must occasionally be cleaned from sludge or scale, which may reduce and slow down the flow capacity.