Noun
check valve (plural check valves)
A valve in a pipeline which allows the liquid or gas to flow in one direction only.
Because this water is being forced uphill through the delivery pipe farther than it is falling downhill from the source, the flow slows; when the flow reverses, the delivery check valve closes. Source: Internet
However, not all round or spherical discs are rotors; for example, a ball check valve uses the ball to block reverse flow, but is not a rotor because operating the valve does not involve rotation of the ball. Source: Internet
Glass valves An all-glass check valve Valves made entirely of glass may be used to restrict fluid flows. Source: Internet