Twinwall Bend are for use with Twinwall drainage. This is predominantly used in stormwater applications where the strength of the pipe is key, such as under roads, sports pitches and landscaped areas. Because of their high compressive strength they can also be buried much deeper than standard PVC drainage pipes as they can easily support a greater weight of soil backfill. Twinwall pipes are made from HDPE (high density polyethylene). The outer ribs add compressive strength whilst the smooth inner bore promotes a friction-free flow of water.