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How to Find Leaks in Vinyl Liner Pools

Finding a Leak in your pool can be a dificult task but we have some steps to follow that will make it much easier to find out if you have one.

The first step is to determine how much water the pool is losing. Fill the pool to the proper operating level and mark the water level with tape, marker or crayon. Record the loss in 1/4 of inches, once in the morning and once in the evening for 24 to 48 hrs. As a rule of thumb, losses up to 1/2 inch daily may indicate a combination of evaporation / wind / splash out. Losses up to 1 inch daily more than likely indicate a leak somewhere in the system, more than 2 inches of water loss per day would normally be caused by broken pipe, broken or loose fitting or by a visible hole or tear in the liner. 

  •  Cause 1: “Splash out” is lost through various activities in the pool including diving, water games, etc.
  • Observation: Fill pool to operating level. If water level does not drop on days pool is not used, splash out is the cause.
  • Cure: Warn pool users that splash out is the cause


  •  Cause 2: The loss of 1/4″ (up to 1/2″ during excessive hot or dry periods) of pool water per day is an indication of water loose due to evaporation.
  • Observation: Loss of water to evaporation will be noticeable in the morning as cooler night air causes a higher rate of evaporation than hot sunlight. Wind also contributes to evaporation.
  • Cure: A solar cover placed on the pool at night will reduce nighttime evaporation by as much as 90%.


  • Cause 3: Filtration/Plumbing System. If splash out and evaporation have been eliminated as probable causes of water loss, the next step is to check the filter / plumbing system.
  • Observation: If water loss continues, the leak may be in one of the wall fittings, such as an inlet, skimmer, underwater light, or in the main drain. Us a dye, such as phenol red of a test kit. With the filter turned off, use dye in the suspected area and observe if it is drawn into the leak.
  • Cure A: Check the pipe/hose connections at valves, filter and pump for leaks. If none are found:
  • Cure B: Shut down the filter and plug the skimmer, main drain and all inlets. If water loss ceases, there is leakage somewhere in the piping. Check the lines by pressure testing them.
  • Cure: Allow water level to drop until it stops at either a tear in the liner or at one of the wall fittings, to indicate the leak is there. However, if the water continues to drop below the fittings or light cut-out add water to the pool to maintain pressure on the walls. The leak is at or below the low water level somewhere in the liner.


  • Cause 4: The liner. To locate a small hole in the liner will require someone with diving apparatus to search underwater for the hole. It is important that the pool be operational so the water is absolutely clear for the diver.
  • Observation: Check the entire pool bottom starting at the liner seams and corners. If a particular area is suspect, the leak can be verified using a dye, such as the phenol red of a test kit, in the area and observing if it is drawn in to the hole.
  • Cure: There are a number of underwater adhesives designed for patching vinyl liners without draining the pool; follow the manufacturer’s instructions.
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  1. John says:

    Thanks for the great post. I did exactly what you mentioned and was able to determine that I did have a leak. I also was able to fix it using the adhesive patching.

  2. The Pool Team | Retail & Wholesale says:

    Thanks for the great information, this is something that is going to be very useful in this line of work, something so small, but can give one a huge headache if you don’t know what you are looking for.

  3. Great article! Best one I have found so far on leaks. Keep up the good work!

  4. mario crone says:

    excelent blog on pool line leaks.
    i am assembling a pressure testing tool that i located on your web site.
    please explain or send a drawing to illustrate where and how to add the air pressure fitting to the device.



  5. Scott says:

    Add a second T to the pressure stand. Use a bushing to reduce the size down and add a Schrader valve. Use an air tank to add air pressure to the PVC line.

  6. Dave says:

    The most common reason for a leak is your pool’s plumbing system. You can easily test this as a factor if you pressure test the piping into your pool. Block off the end of the pipe and pressurize it to 20 psi, and mark down where you see any leaks. If you find a leak at a joint, then use some good Teflon tape on the threads of the pipe to seal it. If you find a crack or corrosion in a pipe, replace that section.

    If you don’t find a leak within the plumbing of your pool, then the water is leaking out of the pool itself. You need to inspect the interior of your liner to find any cracks. Do not drain the pool to accomplish this; rather, get as close as you can to the liner and feel out any cracks, holes or sharp bumps in it. If you think you may have found a leak (or more than one), simply squirt some food coloring into the water near it. If the food coloring disappears into the crack, then you have found the cause of your leak.
    If you’ve found a break in your vinyl liner, you can try to use a patching kit to re-seal it, however, often pool owners find that repairing the crack may not go well and cause the whole liner to need replacing.

  7. Sissy says:

    My pool has leaked all the water but about 2 inches and its right at a seam in the liner which is where I think the leak is….How or what do I use to find exactly where the leak is?

  8. Foster says:

    You can try to visually inspect the liner to find the leak. If you cant see it, try using some food coloring & water. You may have to be in the pool. Squirt a tiny bit where you suspect the hole to be. If the dye is pulled into the hole, youve just located it. If you have no luck, you may need top call a professional that has the equipment to find the leak.

  9. Ramonita says:

    We stumbled over here by a different web page and thought I might
    check things out. I like what I see so i am just
    following you. Look forward to finding out about your web
    page yet again.

  10. jim boyette says:

    we cleaned the pool draining the water started filling the pool noticed water coming from under the pool the water level was dropping no leakes around the running of the pool has to be in liner but cannot find it

  11. BObby Fredenburg says:

    I am currently having water loss only when my pump is running. The water is green so I cannot d a traditional test with dyes. What do you suggest in this situation? I have a 32,000 gal in-ground. It was closed for 2 full years before I bought the house that the pool came with. There was no gizmo/ice compensator in the skimmer when I opened the pool, but when I opened the pool, bubble came from every port.

  12. Nora says:

    Hello, This is Magnificent work ! And will personally recommend it to my friends.
    Thanks a zillion and please keep up the rewarding work. Regards!

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