Preparation and Removing Old Light
Turn the electrical breaker off for the pool light, and make sure that the GFCI and pool light switch is also off.
Assemble the new light according to the manufacturer's directions and check the seals for water tightness by submerging the light under water and checking for bubbles.
Remove the cover from the junction box where the light switch is located. Disconnect the three-conductor electric cord from the switch.
Tape one end of the rope to the end of the electric cord, using a small piece of duct tape. Make sure that the cord and rope will slide down into conduit tube that runs from the junction box to the pool.
Remove the old light from the niche in the pool by locating and unscrewing the pilot screw that holds the light in place. The pilot screw is usually at the top of the light fixture.
Pull the light fixture out of the niche and bring it up onto the pool deck. Slowly pull the electric cord out through the niche. You should see the rope being pulled down into the conduit tube in the junction box.
Continue to pull the electric cord out until you reach the rope. The rope should now be pulled all the way through the conduit tube, with one end out of the junction box and the other coming out of the niche in the pool and up onto the pool deck.
Installing the New Light
Lay the new pool light out and locate the end of the three-conductor electric cord. Cut the rope off of the cord on the old light fixture and attach it to the cord on new light fixture with a small piece of duct tape.
Locate the other end of the rope at the junction box and pull it through the box so that the new electric cord is pulled down into the pool niche, and up through the conduit tube and into the junction box. Remove the rope from the cord.
Leave enough excess cord, approximately 6 feet from the niche in the pool to the light fixture, so you'll be able to raise the light to the deck for service. Cut any excess after allowing for the connection to the light switch in the junction box.
Connect the grounding wire (green or bare copper) to the green ground wire from the light fixture. Connect the line supply wire (black) to the black wire from the light fixture and connect the neutral supply wire (white) to the white wire from the light fixture. Replace the junction box cover.
Turn the breaker back on to the pool light, and reset the GFCI switch to on. Flip the light switch on and then off quickly to ensure that the light is working properly. Do not leave the light on for more than a few seconds as this can cause the light to overheat when it is not submerged in water.
Wrap the excess cord around the light fixture or coil it into the niche so that it fits behind the light fixture. Place the fixture into the niche, with the rim screw at the top. Screw the light securely into place.