This standard covers materials and installation procedures for polyethylene encasement to be applied to underground installations of ductile-iron pipe. This standard also may be used for polyethylene encasement of fittings, valves, and other appurtenances to ductile-iron pipe systems. The major revisions in this edition of ANSI/AWWA C105/A21.5-99 include the following: the format has been changed to AWWA standard style; Section II.D, Copper Service Connections,was added to the Foreward of the standard; definitions of parties and types of polyethylene film were added to Sec. 3; changes to Sec. 4.1, Materials, include deletion of low-density polyethylene film, addition of linear low-density polyethylene film and appropriate material requirements and physical properties, increasing the tensile strength requirement for the high-density, crosslaminated polyethylene film, addition of impact and tear resistance requirements for both polyethylene materials, deletion of the minus tolerance on film thickness for both materials, and addition of an ultraviolet inhibitor, any natural or colored film except black film containing carbon block; Sec. 4.3, Marking, was added to facilitate traceability and to help ensure compliance with the standard; in Sec. 4.4.2.2, Method B, an alternate method of using a 3-ft sheet of polyethylene rather than a 3-ft length of polyethylene tube for joint makeup was added; Sec. 5.1, Inspection and certification by Manufacturer, was also added to help ensure compliance with this standard; and, in appendix A, a new paragraph on stray current corrosion and a new section on uniquely severe environments were added. Additionally, the resistivity ranges in Table A.1, Soil Test Evaluation, were increased to make the procedure more conservative.