Insuring liquid or vapor from tanks cannot flow back through air pipes in case of air flow loss with Leveldatic Non-Return Valves. Backflow may also be a risk if the cabinets are located below the top of the measuring line in the tanks. Can be delivered with internally threaded, externally threaded or flanged tank connection. The Non-Return Valves come in stainless steel and aluminum versions. Uses British Standard Pipe (BSP) for interconnecting pipes. Works with all LevelDatic products.