Leaking Pool Light Repair
If you have a leak or unexplained water loss in your swimming pool you have probably already heard that pool lights are a very common place for leaks to originate. This article is intended to help you understand why pool lights in particular tend to leak, and what you can do about this if you suspect that your pool light might be leaking. There are a few ways that a pool light could possibly leak, however there is one very common way that accounts for most of the leaking pool lights out there, and this relates specifically to the cord seal where the electrical conduit connects to the back side of the light niche.
Before we get too far into exploring the technical reasons that pool lights tend to leak you need to first understand that there are a lot of different kinds of pool lights on the market. The ones that are installed today are different than the ones sold 10 years ago, and those are almost unrecognizable to the ones sold 25 years ago. It is possible that your light will look different than the ones detailed on this page, but all lights still struggle with the same process of mechanically connecting a wire through a conduit which connects to an underwater light fixture. It is hard to pass a wire through a conduit but still be able to create a water tight seal on the place where the wire penetrates.
Safety considerations - Pool lights can sometimes be low voltage like 12 or 14 volts, or they can also sometimes be line voltage of 120 volts depending on where you live and how old your pool is. Any electrical circuit running to a pool light should be GFI protected, however this is not a guarantee that yours is, especially on older swimming pools. Water and electricity do not mix, and adding inexperienced hands to the mix is simply asking for trouble. Speak to an electrician if you have even the slightest concern about whether your pool light is installed safely or not. For this example let's assume you just had the electrical authority out to inspect your pool and they told you the light is safe, but might be leaking. They are an electrical authority after all, and not leak detection and repair people, so you would be left in this situation knowing your light is safe to be around and inspect, but you have reason to believe it is leaking. Breaker for the light gets turned off and you can now proceed with your light leak repair.
Should water be able to get into the electrical conduit?
The answer to this is an unsatisfactory maybe because it depends on the type of light you have and how your pool was built. Some lights anticipate water in the electrical conduit and the electrical conduit runs as much as four feet above water level before terminating with a junction box.
Some pools have a junction box in the deck of the pool, or a deck box as it is called, directly above the pool light location. This is actually good from the perspective of should you ever need to remove the light, having a short pull for the wire would be a huge help. This is not something you should be doing, but it is important to understand that some lights can be a real pain to work on, and if I see your closest junction box for the light is 50 or more feet from the pool then I am seriously doubting that I, or anyone, will be able to pull that existing light wire out, let alone pull a new one in. This is one of the reasons why pool workers and electricians do not readily line up to bid for pool light jobs. They can be a lot of work and you won't really know until you get started.
There is a lot of technical consideration here when talking about leaking pool lights in a general sense and I am worried that I am straying too far here but I need you to appreciate that there are a lot of different configurations out there that you could have, and this just muddies the waters further when you are trying to find a solution to water loss in your pool. Some lights have water in the conduit and some do not. Some lights have a cord stopper or water seal on them, some do not. Some used to but it failed over time. Some people use epoxy, JB Weld or some other form of permanent attempt to seal the cord. This should absolutely never be done. You must not choose a repair that prevents further service to the light being possible. That was so important I am going to say it again:
You must not choose a repair that prevents further service to the light being possible
Whether your pool light was installed with the intention of water accessing the electrical conduit or not, it surely can be said that it would be safer, and preferable, to not have water in that conduit. This is just a leak point waiting to happen. Electrical conduit is small, thinner and weaker than pool plumbing schedule 40 PVC. A 1/2" or 3/4" electrical conduit might be schedule 40 as well however if you do not support and properly bed a pipe that small it will easily bend and snap under a misplaced footstep, or a wheelbarrow of gravel being dumped on it. The electrical conduit pipe itself is a really major concern just because it would be easy to break it for sure, but even still there is a bigger weak link in many pools.
Close nipples - Pardon me? Close nipples are what you call the threaded adapter that you might use to connect something like a PVC electrical conduit to the female threads of a stainless steel light niche, for example. You could use a PVC threaded male adapter with some thread sealant that is 3/4" or so in size, most commonly, and this would enable you to glue your PVC electrical conduit straight into the light niche now. If you did that, like many builders do, you just built a fatal flaw into your pool design. Or at least a weak link to be sure. The sheer force that this fitting accepts as being the transition point between your light niche, which is unmovably attatched to the pool wall, and the electrical conduit, which moves readily in the ground as the earth around your pool settles over time.
A PVC male adapter is very likely to sheer off with the movement and settling of the ground around a swimming pool, leaving a huge potential for leaks in any pool. If your pool is the kind where the light conduit is supposed to have water in it, then you now have a lot of water missing from your swimming pool. So what is the solution to this problem? First, do not transition to a light niche with a PVC male adapter, but instead use a brass close nipple which transitions to a PVC threaded female adapter. This alternative way to accomplish the same transition does cost more money, brass is always more money, but this is money well spent in the interest of building a pool that will hold water in the long term. The brass close nipple will not shear like the PVC male adapter, and the female PVC adapter is an outside fit, not an inside thread, making it inherently stronger by design.
The problems with leaking pool lights do not stop there. This is just the low hanging fruit of why your pool is losing water through the light niche or electrical conduit. Another major problem relates to changes in the composition of the electrical cord itself over time. The cord for pool lights tends to take on water and swell in size over time and this changes the way that the cord fits into the electrical conduit. If there was something temporary like silicone used to seal the wire in the conduit (don't use silicone, definitely not the right product for this job) then changes in the light cord likely broke the weak seal that the silicone had once made and now the water readily leaks past the silicone blob in your light. Water is hard to stop. Silicone was never the right choice for this job.
Duct seal compound - One of the very best lines of defense against a pool light leaking from the cord seal, or leaking from a broken electrical conduit, would be to use a non-hardening duct seal compound to pack around the cord location. This compound is like a dense playdough and it will not shrink, harden or crack over time so if you can manage to get a good amount on, in and around the point where the cord from your light exits the niche then you can effectively stem the flow of water loss here. I would hesitate to call this "fixed" but I can tell you that there are many pools that are permanently fixed with this temporary repair.
Butyl rubber tape - Butyl tape is extremely sticky and will not harden over time making it a suitable choice for a repair to the cord leaving your light niche. Ideally you will be able to wrap the cord with butyl tape and then sleeve some of the tape down into the hole and around the wire on all sides. The more the better in this case. After this you would continue to wrap the end of the light cord with butyl tape, attempting to seal the cord to the niche. The wire needs to be able to move as you reinstall the light, and so you need some extra butyl tape around the light and cord exit point to account for this slight movement without inducing another leak. A cord seal for your light effectively made with butyl tape is another temporary repair that can end up working long term in a best case scenario.
Cord Stopper - This solution is a little more technically challenging than the two above but i definitely like the idea of adding a cord seal to the light if the existing one has failed. The technical challenge here is that each light has a different size cord, and you need an exact fit for the repair to work with your new stopper. Also you need to consider that the light cord might have swollen over time and what should be a nice fit is a total no-go once you get started. There are a few cord seal gaskets which have a slice up the side like this split cord seal to facilitate installing on a light without disconnecting it electrically and pulling out the cord, which is definitely an advantage though this does leave the door open a small amount more than a perfectly installed cord seal without a slice...but pulling out your old light simply might not be an option. I mean, it should be easy enough to pull out and pull back in with fish tapes, or more commonly by pulling a wire pull string along with the wire when you pull it out. Then you can simply pull the wire in again after you have put the cord seal on the wire. Sounds easy. It's not a lot of the time. Here is another example of the split style cord seal for a popular brand off pool light: Pentair cord seal grommet .
Pool lights can be impossible to pull out of the conduit sometimes and when this happens major surgery to your pool deck may be required. You might have to partially drain your pool to access the light from both sides...it gets out of hand pretty quickly. Even something as simple as the original installer using dish soap instead of wire pulling lubricant to pull the wire through the conduit means you will likely never get the wire out.
Dried soap increases the friction tenfold in the pipe and all but the shortest pipe runs will not pull out no matter how hard you pull. For this reason I am inclined to advise to use a split cord seal instead of attempting to disconnect or pull your lights out. You could easily cause a problem with the light cord that requires you to buy a new (expensive) light right away, plus now you need to disconnect the electrical connections for the light which means you should be speaking to an electrician. A split gasket can go on to the light cord (and often bonding wire cord) and then be wedged into the niche conduit exit point to stop a leak from this location. For my money I would use both a new cord seal stopper, but also the duct seal compound to ensure that I was getting a leak free seal, or at least as close as you can get with a bandaid type repair like this.
In an ideal world you should get a new light, or a new cord seal, or both, and have the GFI and bonding for your light verified at the same time. Pool safety is definitely worth the expense and a leaking pool light is not a problem you can simply ignore. Unfortunately with limited repair options, or at least limited affordable repair options, pool owners will look to cheaper methods to stem the flow of water through faults in their light. If you use the duct seal, butyl tape or new cord seals as mentioned in this article you will be vastly further ahead than if you attempt to ignore the problem, or use the wrong product like silicone, JB weld or epoxy to try to fix this leak.
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