How to replace a light fixture
When a conventional pool light fixture rusts out or otherwise fails, it will have to be replaced. If the light continually trips the GFCI, there’s a good chance it has developed a short in the fixture and wiring. At this point, the entire fixture and wiring will have to be replaced. The following steps will describe how this is done.
1. Locate the junction box.
Turn off the power source at the braker. Find the j-box.
With older pools, this will be in the deck, directly above the light niche. More recent building codes required that the j-box be at least 5 feet from the water edge and 18 inches above the water surface so check the garden behind the light niche.
2. Remove the screws attaching the cover plate.
Three wires come into the box from the breaker and three go out of the box to the light fixture. The three to the light fixture are insulated and colored white, black and green and are bound with a waterproof sheathe. Disconnect the three wires and unscrew the cord clamp.
3. Remove the light fixture.
Lean into the pool and remove the retaining screw from the faceplate that holds the fixture to the niche.
The bottom of the fixture is hooked into the niche and can be lifted out.
4. Uncoil the excess cord.
Uncoil the excess cord to provide enough slack to raise the fixture out of the niche. Go to the j-box and pull on the cord to the fixture. If the cord moves at the fixture, the replacement will be simple. If the cord does not move, it may help to pour a little tile soap down the conduit at the j-box and allow it to sit overnight to grease up the cord for easier removal.
Some service techs use oil but remember that whatever is used to lubricate the cord will eventually wind up in the pool.
5. Cut the cord where it enters the old fixture.
Strip off the rubber sheathe by about 6 inches. Remove the string or paper threads that run along the wires. Remove the insulation from each wire by about 6 inches
6. Remove the new fixture from the box.
Take the wires of the new fixture and strip the insulation by about 6 inches. Bind the wires of the new fixture to those of the old, taping the set with electrical tape that is no thicker than the cord itself or it won’t pass easily through the conduit. The goal is to create a union that will not separate when pulled.
7. Lay the cord in the water.
Return to the j-box and pull the old cord until the new cord arrives there. Keep pulling until there is enough cord slack at the fixture for it to easily reach onto the deck for future bulb changing. Untape the new wires from the old at the j-box.
8. Finish at the light niche.
At the light niche reach into the pool and coil excess line around the fixture and set the fixture into the niche.
Screw the lock screw at the top.
Credit: Swimming Pools, Spas, Hot Tubs, Fountains, and Similar Installations: Mike Holt: Article 680, based on the 2017 NEC.