By code, all electrical pool devices, lights, pumps, control boxes etc., must be tied into (or bonded to) a common grid that surrounds the pool. When the pool is built, it will incorporate a continuous steel rebar grid within the concrete pool wall. This grid is grounded into the earth and all electrical units, like the light niche show here, are wired with heavy 8 gage wire to this grid. This is referred to as bonding. This guide shows how to add a new bonding wire to this grid when you are adding a new electrical unit to your pool system.