polybutylene is a type of plastic resin that was used extensively in the manufacture of potable water piping from 1978 until 1995 shell and dupont were two of the primary manufacturers of the polybutylene also known as pb piping and fittingsolybutylene is a type of plastic resin that was used extensively in the manufacture of potable water piping from 1978 until 1995 shell and dupont were two of the primary manufacturers of the polybutylene also known as pb piping and fittings