A sump line is designed to extract water from underneath the pool. Every pool will require a sump line for a warranty to be redeemable and valid.  This one featured is the simplest one to be installed and used. This particular installation is done with an 8" PVC pipe, one piece of drain pipe, an end cap, a drain line sock, and a fitting to connect the 8" PCV pipe to the drain pipe. When assembled, as shown in pictures, bury in gravel.