1.1 ,This guide will discuss standard practices which have been successfully utilized in the field for over 35 years to provide external corrosion protection of polyethylene encased ductile iron pipe supplemented with cathodic protection (CP). This guide may also be used for ductile iron fittings, valves, and other appurtenances specific to ductile iron pipe systems. Case histories and publications reporting on the use of cathodic protection to supplement polyethylene encasement are included as an Appendix in this guide.