The roof overflow drain is usually set at 20-30cm above the flat downpipe to avoid excessive water flow in the roof area.When the water level is higher than the overflow outlet, the overflow outlet drainage system will start working and together with the original roof drain to relieve the roof drainage pressure in time.The overflow outlet developed and designed by JUAL for single-layer roofs,prefabricated and integrated in the factory, provide a safe, reliable and convenient installation method for the site. The construction is efficient and fast. It can be integrated with any kind of TPO/PVC .