Protect sewage systems and ground water from serious contamination. Vetter pipe sealing bags FS help your team stop hazardous substances quickly. With Vetter bypass bags, you can dam up hazardous liquids and gases and divert them controlled using a fire hose. Vetter’s pipe sealing bags and bypass bags FS were specifically designed and developed for fire services. The bags individually adjust to different line diameters and are especially resistant to chemicals as well as heat.