Wafer Dual Plate Check Valve

check valve
A mechanical device in a pipe that permits the flow of water or air in one direction only.
A valve that closes to prevent backward flow of liquid
Limits the flow of gas to one direction only. Use a check valve between the bubbler and generator to prevent unwanted pressure build up in the generator, and a safety against a low level bubbler. A check valve, such as used on torches, is recommended.
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.

wafer
a small adhesive disk of paste; used to seal letters
a small thin crisp cake or cookie
Fasten or seal (a letter, document, etc.) with a wafer
thin disk of unleavened bread used in a religious service (especially in the celebration of the Eucharist)

plate
a sheet of metal or wood or glass or plastic
Cover (an object) with plates of metal for decoration, protection, or strength
Cover (a metal object) with a thin coating or film of a different metal
Serve or arrange (food) on a plate or plates before a meal
coat with a layer of metal; "plate spoons with silver"
home plate: (baseball) base consisting of a rubber slab where the batter stands; it must be touched by a base runner in order to score; "he ruled that the runner failed to touch home"

dual
Consisting of two parts, elements, or aspects
double: consisting of or involving two parts or components usually in pairs; "an egg with a double yolk"; "a double (binary) star"; "double doors"; "dual controls for pilot and copilot"; "duple (or double) time consists of two (or a multiple of two) beats to a measure"
(in an aircraft) Using dual controls
double: having more than one decidedly dissimilar aspects or qualities; "a double (or dual) role for an actor"; "the office of a clergyman is twofold; public preaching and private influence"- R.W.Emerson; "every episode has its double and treble meaning"-Frederick Harrison
(in some languages) Denoting an inflection that refers to exactly two people or things (as distinct from singular and plural)
a grammatical number category referring to two items or units as opposed to one item (singular) or more than two items (plural); "ancient Greek had the dual form but it has merged with the plural form in modern Greek"