A swing check valve is mounted with a disc that swings on a hinge or shaft. The disc swings off the seat to allow forward flow, and when the flow is stopped, the disc swings back onto the seat to block reverse flow. The weight of the disc and the return flow has an impact on the shut-off characteristics of the valve. Often a lever and weight or a lever and spring are mounted to achieve optimum performance. Swing check valves with lever and weight are appropriate for installations with an increased risk of water hammer at standard velocities. Swing check valves with lever and external spring are suitable for high pressure, insufficient backpressure, and high flow velocities. An important thing to be aware of when installing a swing check valve is that it is not entirely maintenance-free since the disc needs to be cleaned once in a while. Furthermore, a lever is often mounted to enable visual check. Therefore, swing check valves are often installed where personnel is present.