Twinwall flap valve suitable for 150mm, 225mm and 300mm JFC twinwall. May not fit other manufacturer's twinwall products.
Flap valves allow water to flow out of the system, but prevent back flow, stopping water flowing into the system through the valve. Ideally used if the drainage system is located near homes, buildings, or areas liable to flooding.
Manufactured from PE to prevent corrosion.