Polyvinyl chloride
About half of the polyvinyl chloride resin manufactured each year is used to make pipes. PVC pipes are 66% of the newer water pipes in the US.  PVC pipes are 75% of new sewer pipes. PVC is useful because of its light weight, high strength, and low reactivity. Also, PVC pipes can be glued together, or they can be connected by heating (similar to joining HDPE pipe). Both kinds of connections make permanent joints that do not leak.