A Check valve secures that water only streams in a single direction of a plumbing system in order to prevent polluted water from flowing back into the system after it was already used. A swing check is the most common type of check valves that includes a hinged panel which opens and closes as liquid flows through it. While liquid enters a swing check, the pressure increases and the hinged panel raises up. This allows the liquid to flow through and exit the system. The check valve hinge is represented as a one way stream and liquid is not able to flow through in the opposite direction.