Pool lighting loses brightness or fails outright over the years — and unlike an ordinary light bulb at home, it involves equipment underwater, powered at low voltage through a separate transformer. Knowing which part actually failed saves an unnecessary replacement of a more expensive component.
Most common causes of failure
- An end-of-life LED bulb or module — gradual dimming, a colour shift, or one light going out completely while others keep working.
- A faulty transformer — none of the lights on the same transformer work, even though the bulbs themselves are fine.
- Moisture inside the fixture housing — with older or damaged seals, moisture can cause a short circuit or contact corrosion.
- A damaged cable between the transformer and the fixture, often from mechanical damage during other work around the pool.
How to tell a bulb fault from a transformer fault
If only one light out of several on a shared transformer doesn’t work, the problem is likely in that specific fixture or bulb. If all the lights on the same circuit fail at once, suspicion falls on the transformer or the supply cabling. A multimeter can confirm whether the transformer’s output actually delivers the voltage shown on its label.
Step-by-step LED bulb/module replacement
- Turn off power to the lighting at the breaker, not just the switch.
- Remove the fixture from its niche — on most pool fixtures, loosening a single retaining screw lets you pull the fixture out along with its cable, clear of the water.
- Open the sealed housing and replace the LED module with a type matching the original’s voltage and base.
- Check and, if needed, replace the housing’s sealing O-ring — the same principle as with other pool equipment: renew old seals while you’re already there.
- Return the fixture to its niche and secure it with the screw only after confirming it works outside the water.
When to call an electrician instead
Replacing the transformer or repairing damaged supply cable involves mains-related wiring and should be handled by a suitably qualified person — it’s electrical work in direct proximity to water, where a wiring mistake is a real safety risk.
FAQ
Can I replace the bulb without draining the pool?
Yes, standard pool fixtures are designed to be pulled from their niche along with the cable without draining — the bulb replacement itself then happens out of the water.
Why does the new LED light shine a different colour than the original?
Different manufacturers use slightly different white tones or colour spectrums — for a match, it’s best to use the same manufacturer and model as the original.
How long does a pool LED bulb last?
Roughly several years under normal operation, but life is shortened by frequent on/off switching and operation in an overheated niche without sufficient water cooling.
Replacement LED modules, transformers, and lighting accessories are in the pool technology category. More articles on pool technology are in the Guides section.
