Septic tanks are devices designed for the treatment and filtration of feces. The principle involves the decomposition of solid matter at the bottom of the tank, while the water-soluble substances rise to the top and are flushed out through pipes, preventing blockages. This allows for sufficient time for the solid matter (such as feces and waste) to undergo hydrolysis. A septic tank is a small treatment structure that separates and sedimentates domestic wastewater and anaerobically digests sludge..

Manhole: A vertical shaft constructed at regular intervals along the underground pipeline location. Primarily used for pipeline maintenance, sludge removal, and to connect pipelines of different directions and heights. Specific types include flushing manholes, street manholes, water-diversion manholes, and wastewater manholes. Manholes are conveniently installed for the maintenance of urban underground infrastructure, such as electricity, water supply, drainage, sewage, communication, cable TV, gas pipelines, and streetlight circuits.