Sewage Check Valves

check valves
(Check valve) A check valve, clack valve, non-return valve or one-way valve is a mechanical device, a valve, which normally allows fluid (liquid or gas) to flow through it in only one direction.
(Check valve) used to provide flow through a pipe in one direction only. When installed between an external filter and the pond, it keeps the dirty water in the filter from flowing back into the pond if power is lost. They are also used to keep an external pump primed if power is lost.
(Check valve) A device inserted into a moving liquid stream that allows flow of the stream in only one direction; most often used on the inlet and outlet sides of an HPLC pump.
A valve that closes to prevent backward flow of liquid

sewage
Waste water and excrement conveyed in sewers
waste matter carried away in sewers or drains
Sewage is water-carried wastes, in either solution or suspension, that is intended to flow away from a community. Also known as wastewater flows, sewage is the used water supply of the community. It is more than 99.
A suspension of water and solid waste, transported by sewers to be disposed of or processed; sewerage