Leaking pool skimmers are one of the most common types of leaks in a vinyl liner pool, and also usually the easiest pool leak to find and fix. Skimmer leaks are easy to find because the water will always drop to the bottom of the skimmer and then the leak stops.
To see if the water level stabilizes at the skimmer, you'll need to turn the pump off, or just close the skimmer valve(s) and run the pump on the drain only.
If your pool leak stops or slows at the bottom of the skimmer opening and does not go any lower then you likely have a leaking skimmer.
IS THE LEAK IN THE PIPE? This is everyone's worst and first fear - that they'll have to rip up the deck and replace the pipe - however this is very rarely the case. If the leak is in the skimmer pipe (and not the skimmer itself), it may leak more when the pump is off, because when the pump is on the pipe is under a vacuum. Another indicator of a pipe problem is that you may see air coming into the pump basket or bubbles in the pool returns when the pump is running.
The easiest way to see if you have a leak in the skimmer line or the skimmer is to plug the skimmer and close the skimmer valve in front of the pump. If the pool stops leaking, then you know it's somewhere in the pipe between the skimmer and the pump.
IS THE LEAK IN THE SKIMMER? Plug in the skimmer and slowly put some red food coloring around the skimmer faceplate, and see if the dye is sucked in. If yes, then you have a bad gasket or loose screws on the faceplate. If no, inspect the skimmer closely for any hair line cracks in the body or throat, and dye test any suspicious areas.
FIXING A LEAKING POOL SKIMMER: Here are some of the things you will have to do to repair the leak depending on what you found. If the leak is in the pipe between the skimmer and the pump in some cases the easiest thing to do is basically dig a new trench and put in a new line. You do not need to unearth the old pipe, just abandon it and lay a new pipe that is connected to the skimmer on one end and the pump on the other end. Be sure to dig it below the freeze line, which is 12"-36", depending on how far north you are.
On the other hand, if the pipe is not very old, you can use Geophones or other listening devices to pinpoint an underground pipe leak when the pipe is pressurized, usually with water and air. The advantage to this is that with proper equipment, you can find the exact point of an underground crack in a pipe, and dig down and replace a short section of pipe. It may be best to call in a local leak detection company to pinpoint the location for you.
If you do see a crack in the skimmer, you can use Pool Putty, or any underwater epoxy putty. Just mix up equal amounts of resin and hardener and push it into cracks, using water to smooth it out. Waterproof, and dries underwater - very easy to use.
REPLACING A POOL SKIMMER: Not usually necessary, unless the skimmer itself is severely cracked and damaged. Zach wrote a post about how to replace a pool skimmer, if your skimmer needs to be replaced.
SKIMMER WALL REPAIR: On vinyl pool skimmers that have been leaking around the faceplate for years, rust and corrosion can damage the pool wall and the liner. If the wall area around the skimmer is rotted or rusted through you can use JB Weld to resurface a rusted wall, or you can use sheet metal to reinforce the area. If you use JB Weld, mark the holes in the pool wall for the skimmer screws to go through. Replace with a complete new skimmer, they aren't expensive. If you keep the existing skimmer, replace both the faceplate & gaskets (under the liner and on top of the liner). As added liner protection, cover rusty or patched walls with wall foam.
NEW FACEPLATE AND GASKETS: In some cases, just replacing the skimmer faceplate and gasket will solve a leaking skimmer problem. Many vinyl pool skimmer leaks are caused by a skimmer faceplate that is not on tightly enough.
To prevent this preventable problem, install your faceplate with a large #3 Phillips screwdriver, and if you do not work out regularly, call over a friend with muscles to really crank on the screwdriver, tightening very hard - until you hear the plastic begin to creak and moan.
No matter what you have to do to find and fix a pool skimmer leak, if you are losing water - it has to be done. Leaking skimmers not only waste heated and treated water, but can damage walls or erode backfill that supports the walls and deck.
FIX-A LEAK: We sell a product called Fix-A-Leak, that is a liquid added to pool that seeks out and fills small cracks and voids. It does work, on SMALL cracks and voids, but in my opinion, it's better to find and fix the skimmer leak. Where skimmer leaks are concerned, it's best to make a solid repair, and not rely on a product that may not work, or may only work for a short time.
SPP Pool Expert