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    Leak Detection in an Inground Vinyl Pool

    December 18, 2012


    Is your pool leaking? Leaks in a vinyl liner can cause a host of problems. If leaking during winter, and your pool is closed and covered, the pool cover can be damaged or be pulled into the pool. If not refilled, and the water level goes too low, the vinyl liner can pull away from the pool, causing wrinkles.

    Leaks over a period of time can do some damage to the pool floor. Depending on the severity of the leak, much more damage can be done. Wash outs, indentations and with vermiculite, cracking and flaking can occur. So, it is best to find the leak and take care of it as soon as you can.

    Bucket Test for Pool Leaks

    First, you should determine if you have a leak, or just a lot of evaporation, which can be hundreds of gallons on a warm day. To rule out evaporation, do the bucket test. Take a 5 gallon bucket and inside the bucket mark a line with a permanent marker about 2/3 of the way up. Fill the bucket to the line drawn and set it right next to the pool, or set it in the pool, as shown in the video. Use a piece of duct tape to mark the water level currently in the pool.

    Wait 24 hours and measure from the tape mark to the current water level in the pool and also measure inside the bucket from the mark to the water level. If these are the same it is evaporation and your pool is not losing water from a leak. If the pool loses more water than the bucket loses - you have a leak. https://youtu.be/mS2N5e-nXBw

    Dye Testing for Pool Leaks

    A lot of leak detection in vinyl liner pools is done using a colored dye, to test suspicious areas - to see if the dye gets sucked out of the pool. To dye test small areas, shut the pump off and allow the water to become still. If you see something but are unsure, you can use food coloring, or a dye-testing syringe to dye test any suspicious areas. do not use colored test kit reagents as dye, if you suck water into the bottle you will dilute the reagent, making your test readings false.

    You can dye test around skimmer, light and return faceplates, and around steps and swim outs. For most tests you can lay on the deck and reach a lot of area. Wear a swim mask, so you can see if the dye is getting sucked out. Large leaks are easy to see, but small leaks require still water and close testing. Repeat your tests until you are certain that the dye is being sucked out of the pool.

    Where to Look for a Pool Leak in a Vinyl Pool

    There are many places that inground vinyl liner pools can leak water. The most common places for leaks in an inground pool are around the steps, skimmers, fittings, drains, and of course the liner itself. If the water level drops and seems to stabilize at a particular level, that is a big clue of where to look.

    Steps: And also any swim outs or buddy seats. When these are installed, the liner is cut and a plastic strip is screwed on tight, over a rubber gasket. You can see the strip where the liner ends and the fiberglass step starts. There are 3 sides that could be leaking, both sides and the bottom strip. The best way to check these are with a mask under water, carefully inspecting all 3 sides. Look for any holes, or areas where small leaves have been sucked into a void. Dye test if you are see something that looks 'leaky'. If the step gaskets look bad, you can buy a new vinyl pool step gasket kit.

    Pool Lights: Pool lights on a vinyl pool use a circular plate that is gasketed against the liner and screwed on tightly. You can dye test the light ring by hanging over the pool edge (if your arms are long enough). Lights can also leak at the point where the light cord leaves the pool. For most inground pools that use a light niche, (the sideways 'bucket' that the lamp fits into), the cord exits the niche in the upper rear. The conduit that the cord runs into can be sealed with a light cord plug, pool putty, or silicone - if a leak is suspected. If your water level constantly drops to the top third of the pool light - it's strongly suspected.

    Skimmers: Another place where the vinyl was intentionally cut, the skimmer faceplate and gasketing can be dye tested or inspected for voids or stuff stuck in a crack. Inside the skimmer, look for any cracks in the plastic skimmer throat and skimmer well. Dye test any suspicious areas.

    Return Fittings: Your wall fittings, and the faceplates around them, can be dye tested as well. Remove the eyeball fitting to test inside of the fitting, to try and test the backside.

    If you find any of these gasketed faceplates or strips leaking, order replacement gaskets, do not try to seal it up with silicone or pool putty. The proper fix is to lower the water level below the faceplate, remove all the screws, replace the gasket and faceplate, and the screws very tightly.

    Main Drains: do not forget unless you can plug off your main drains you haven't checked if the leak could be in that line. Usually, to do that you would need a diver with tanks to plug that line, or someone who can hold their breath very well - so that would be the last alternative if everything else has not found your leak. Leaks in main drains are hard to fix, and for this reason, leaking main drains are commonly abandoned. Some adjustment to circulation or filtration is usually needed to make up for the missing main drain.

    Pool Liner: After checking all the above and not finding any leak it is time to eliminate the pool liner. Shut off the pump, and take any time clocks off line. Plug with pool plugs your skimmers and inlet fittings and mark the water level with duct tape. Wait 24 hours to see if water level drops, do not forget some small amount may be due to evaporation - note how much water was lost in the bucket test. With the lines plugged, if your pool water drops more than evaporation, we can rule out the plumbing, and look again at the pool shell.

    If the leak is in the liner, other than going over every square inch of the pool - there is no easy alternative. A diver is best for this task, if you can't find it by looking yourself around the edge carefully. Keep in mind, there can always be more than one leak. This is something you may not know until you fix a leak you find and see if water has stopped dropping.

    If your leak detection process stretches out over several days, you may need to shock, brush and skim the pool during this time that your filter is off, to keep your water fresh. [/notice]

    Plumbing Pool Leaks: If the water does not drop (with all of the lines plugged) then your leak is probably in the lines. Make sure it's not leaking out of the backwash line, or somewhere aboveground on your pump and filter equipment.

    Leaks in underground pipes are rare, but they do happen. To determine which line it is , a process of elimination can be used to isolate different lines. Pressure testing individual pipes can determine with certainty which pipe is leaking. Sometimes it is easier to replace the line which is bad rather than trying to pinpoint the exact location.

    Patching Pool Leaks: Small tears or rips up to several inches in length can be patched with a vinyl patch kit, or you can use a flexible liquid sealer, that squeezes out of a tube. Small leaks in vinyl liners or pipes can be fixed using Fix-A-Leak.

    When to Call in the Pros

    To find out exactly where an underground leak might be you may have to call in someone who specializes in leak detection. They have specialized equipment for finding pipe leak locations and liner leak locations. Look under swimming pools in the yellow pages, or search for pool leak detection for your local area. Depending on what you ask them to do, leak detection companies may charge between $250-$450.

    Hoping you won't need to go that route however! Most pool leaks are simple to fix - once you find them! And the majority of leaks in a swimming pool do not involve ripping up any concrete, or any major repairs.

    Happy Hunting!

    Larry Weinberg
    SPP Pool Expert

    Blog Author