Althon HDPE Flap Valves can be used in Surface, Sewer and Water Process applications. They are a Simple and Highly Effective way to Prevent Water Backflow into a system. The 600 – 1500mm Range of Flap Valves has additional features when compared to the smaller sizes such as Welded Stiffening Ribs. Our Flap Valves are manufactured in HDPE and Stainless Steel 316. Althon HDPE Flap Valves are Lightweight and High Strength. Our Flap valves are therefore Easy to Install, Responsive and very Reliable.