Bolted sleeve-type couplings offer no internal resistance to longitudinal thrust forces. Such forces must be mitigated by other means, or the coupling must be restrained externally via harness bolts and attached restraint lugs. Whether restrained or unrestrained, these couplings can be configured to provide electrical isolation between the two adjacent coupled pipe ends. When electrical isolation is required, the couplings are furnished with one or two rubber “boots” that are placed on the pipe end(s) to halt the flow of electrical current between the adjacent pipes. Harnessed couplings requiring electrical isolation also require washer/sleeve insulation inserts at the connection of the harness bolts to the restraint lugs. Requirements for bolted sleeve-type couplings are defined in AWWA C219. Requirements for external harness restraint are defined in Steel Water Pipe: A Guide for Design and Installation, AWWA M11.
