Should restrained joints always be used when installing pressurized Ductile Iron pipe through a casing pipe?
No. ANSI/AWWA C600 Standard does not contain this requirement but does provide guidance for casing/carrier pipe installations. Casing pipes should normally be 6- to 8-inches larger than the outside diameter of the Ductile Iron pipe bells. Insulating chocks, skids, or spacers normally should be placed on the Ductile Iron pipe (carrier pipe), or affixed to the casing, to ensure approximate centering of the carrier pipe within the casing pipe. In order to further stabilize the Ductile Iron pipe, normally the area between the casing pipe and the carrier pipe is partially filled with sand or grout. Such installations stabilize the Ductile Iron pipe and minimize any movement, flotation, or “snaking” that might occur within the casing pipe, with other influences outstanding. If the annulus is completely filled, it can be argued that external loads might understandably be transferred to the carrier pipe. If restrained joints are needed to resist thrust forces on a Ductile Iron pipeline (for ex
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