Underground Installation Procedures

             The trench should be wide enough to assemble the joints. Total load on the pipe includes both earth load and the truck load. For additional information refer to CISPI's "Trenching Recommendations for Cast Iron Soil Pipe" brochure. Safety procedures in trenching should be observed, including provisions to avoid collapse of the trench wall. 

             The trench bottom should be stable enough to support the complete barrel of the pipe. If possible the barrel should rest on even and undisturbed soil. In certain conditions, i.e. rocky, it becomes necessary to excavate deeper than needed, place and tamp back fill material to provide an appropriate bed. Holes should be provided at each joint for the hub or couplings to allow for continuous support of the barrel along the trench bottom. If the ditch must be excavated deeper than the depth of the drainage pipe, place and tamp backfill material to provide uniform support for the pipe barrel. 

             Many times in the installation of underground soil pipe it is necessary to change the direction of the line. Cast iron soil pipe will allow this through deflection in the joints. Installation should initially be completed in a straight line and then deflected to the appropriate amount. Maximum deflections should not exceed 1/2 inch per foot of pipe. This would allow 5 inches of deflection for a 10 foot piece of soil pipe and 2 1/2 inches for 5 foot pipe. For changes in direction greater than these deflections an appropriate fitting should be used. 

             Once installation (For joining methods refer to Part 3) is completed, the underground section is ready for test. Because this portion of the system is usually the largest diameter pipe it may be necessary to restrain the system or joints from movement prior to testing. This may be done by partially backfilling and leaving the joints exposed for inspection, or rodding and or bracing. 

             After testing is completed, the trench can be properly backfilled. When backfilling care should be taken to protect the pipe from large rocks, stones, or frozen fill material etc., that could damage the pipe. Cast iron soil pipe laid on a solid trench bottom requires no tedious placement of selected backfill materials. 

             Installers should always consider local conditions, codes, manufacturer instructions, and architect/engineer instructions in any installation.