... HS41X-16A anti-fouling off valve (pipe backflow prevention device) is used to prevent pollution of raw water piping back safety ... safety of drinking water. HS41X-16A secure antifouling off valve is added between the two valve composed of a drainage device ... , valve cover, valve, gaskets, springs and other components. Drainage is mainly from the valve, diaphragm valve cover, valve, seal plate, valve, ...