Mufa PEHD Rainplus 125 PEHD Rainplus 125 is a type of plastic piping used in outdoor plumbing applications. It is made of high-density polyethylene (HDPE) and is designed to be durable and resistant to weathering. The pipe has an integrated rubber seal that provides an effective barrier against water infiltration. It is available in a range of sizes and can be used for both above and below ground applications.