100mm 4" PVC Swing Check Valve Suit PVC Pressure Pipe TSWCVS100 is commonly used in water and wastewater applications. A simple operation, the 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 any reverse flow. The weight of the disc and the return flow is what creates the shut-off characteristics of the valve.