How to Find a Leak in a Pool

A pool leak can be a huge problem, causing water wastage, poor water conditions, and expensive utility bills. If your pool is leaking, it’s critical to identify the leak as soon as possible – stopping leaks early saves time and money and prevents damage from progressing further and getting worse. But pool leaks aren’t always obvious due to normal evaporation and can be hard to find. So let’s look at how to find a leak in a pool.

How to Find a Leak in a Pool

Signs Your Pool May Have a Leak

Of course, disappearing water is the first and most obvious sign of a leaking pool. However, water is often lost to evaporation, so a slow leak may not be immediately apparent. In fact, there can be several other signs that you may have a leak, so here are some indicators to look out for:

Cracks or Gaps in the Tile or Bond Beam

When a pool is leaking, it softens the ground around the pool. This may cause cracks or gaps in your tile, or cracks in the bond beam, as the pool settles into the ground.

Wet or Soft Spots in Your Landscaping

Wet, soft, or muddy spots in landscaping are a common sign of a pool leak. Look for uneven growth in the grass or low, wet spots in the garden.

Excess Water Beneath Pool Equipment

Puddles, wet spots, or standing water around a pool pump or pipes is almost certainly an indicator of a leak in your pool equipment.

High Water Bills

Automatic pool fillers can often mask a leak, so you may not notice a problem until you review your water bill. If an auto filler seems to be running more than usual, you may want to check your water bill or your water meter and see if your usage is unusually high.

Dirt or Gurgling in the Pool Return

Leaks in pipes can allow dirt into the pool return or allow air that causes a gurgling sound.

Unstable Water

If a pool is leaking and constantly having new water added, it can make it difficult to maintain stable water chemistry. Likewise, if your water condition is extremely unstable or has ongoing algae problems, a leak may be the culprit.

Naturally, water loss is the first and most obvious sign of a pool leak, but pay attention to these other tell-tale signs. Not only can they alert you to the presence of a possible leak, but they can help you find it.

How to Determine Whether Your Pool is Leaking

If you suspect your pool is leaking, but aren’t sure, here’s a test:

  • Weigh down a bucket with a brick or rock, and place it on your pool steps to sit halfway below the water level in your pool.
  • Fill the bucket with pool water so that the water level inside the bucket is the same as the water level of your pool.
  • Mark the water level inside and outside of the bucket with a sharpie, grease pencil, or a piece of tape.
  • Wait 24 hours without running the pool pump.
  • Check the water level the next day. The water inside the bucket should have evaporated at nearly the same rate as your pool water. If the pool water level is much lower than the water level in the bucket, you probably have a leak.
  • Repeat this test a second time, this time with the pool pump on, and compare the results. Again, if there is much more water loss with the pump running, you may have a leak in the plumbing rather than in the pool shell itself.

Common Sources of Pool Leaks

If your pool is leaking, it’s essential to identify the source as quickly as possible. The most common areas where a pool may leak are:

The Pool Skimmer

Pool skimmers are the most common areas that develop a leak. There may be a gap around the seal, or a crack may have formed. If water falls below the level of the skimmer and the leak stops, or if your pool leaks more when the pump is off, that’s probably the cause.

If you can see air bubbles in the water return or hear gurgling when the pump is running, there may be a leak in the suction side of the skimmer.

Pool Fixtures

Another common place for leaks to develop is around pool features and fixtures like lights and returns. These may have gaps or cracks in their seals, causing a water leak. Like with skimmer leaks, it is common for pools to leak until the water level is below lights or returns and then stops.

Structural Damage in the Pool Shell

If the pool is leaking from the shell itself, the most common cause is structural damage. As the ground settles around a pool, it may cause cracks in concrete, gaps in tile, or tears in the vinyl.

Plumbing Leaks

Underground or under-deck plumbing leaks are common, especially in older pools. Pipes may move as the ground settles, may become damaged or corroded, or develop loose or broken fittings as a pool ages. These types of leaks can be the most difficult to find and fix and usually require the help of a professional.

If you have a pool leak, narrowing down where the leak is coming from will help you address it more quickly. Start with the most likely causes and work from there.

Narrowing Down the Source of a Pool Leak

Once the bucket test indicates the presence of a leak, the next most important thing to identify is whether you have a leak in your pipes and supply lines or whether you have a leak in the pool shell itself. To narrow down the cause of your leak, follow these steps:

  • Use plugs or covers to plug up all the filter and jet fittings in your pool.
  • Seal up the fittings and wait 24 hours. You may want to use the bucket again to measure any water loss.
  • If your pool is still leaking with the filter fittings covered, remove those plugs
  • Use those plugs to block up the water intake and return on your pool skimmer.
  • Wait 24 hours to see if the pool is still leaking with the pool skimmer plugged.
  • If plugging your skimmer line or water fittings stops the water loss, you probably have a leak in your pool water supply or return.

To narrow down the precise source of a leak in your lines, do the following:

  • Turn off all pool pumps and equipment.
  • Use plugs to seal all returns and pipe fittings
  • Remove a single plug, and wait a few minutes for the water to calm
  • Add a drop or two of red food coloring near the return, and see whether the dye flows into a leak
  • Do this systematically for every jet, return, drain, skimmer, etc., using dye or red food coloring to see where a leak creates a water current.

Suppose your leak is in the fixtures or plumbing. In that case, it is usually best to consult a professional to further isolate and address the leak because the equipment can be complicated and difficult to repair. However, narrowing down the source can help you save time when working with a professional.

If you continue to have water loss when plugging your skimmer and returns, you probably have a leak in the pool shell itself.

How to Find a Leak in a Pool

To find a leak in a pool, you will need:

  • A mask, so you can see clearly underwater
  • Red food coloring

Then follow these steps to find the source of your leak:

  • Turn off the pump, skimmer, and other pool equipment and allow the water to be still. Let the pool rest for 15-20 minutes to keep the water as still as possible.
  • Get in the pool, inspect it carefully; look for gaps, cracks, or openings in tile or concrete. Look for missing plaster or grout around drains and fixtures. Feel the pool walls with your hands, looking for soft or weak spots. Walk carefully over the bottom of the pool, feeling for soft spots in a vinyl liner. The most obvious place for leaks is around fixtures and fittings, so check around gaskets, returns, light fixtures, and other features.
  • Hold still and wait for the water to calm, then drop a couple drops of red food coloring into the water near returns and features. Observe whether the food coloring appears to be flowing into a crack or gap.
  • Work your way around the whole pool; feel for weak spots and use red food coloring to see where water is flowing and leaking.

Red food coloring makes water currents visible, allowing you to see where water is leaking from the pool and how quickly it is flowing. Used correctly, it will help you find leaks and determine how severe they are.

Remember that just because you’ve identified one leak doesn’t mean that there aren’t more. Therefore, when performing this test, check the entire pool to make sure that you’ve identified all possible leaks and sources.

What to do About a Leaking Pool

If your pool leaks to a certain level and then stops, the leak is above the water level. For example, it is common for pools to leak until the water is below the skimmer level or light housing and then stop.

However, if you have a vinyl pool, allowing it to dry out above the water line can cause more damage.

If you have a leak in a vinyl pool and have identified where the tear or damage is, make a temporary patch with duct tape (or some other waterproof tape), add water to the pool, and call a professional.

Depending on the type of pool you have and where the leak is located, you may be able to conduct the repairs yourself. For example, seals around fixtures and returns may be repaired with putty or sealants.

Gaps in tile and cement may be repaired, and vinyl can be patched. There is a wide range of products available to help pool owners repair small leaks on their own without the help of a professional.

However, if you can’t identify the leak source, or if your pool is leaking from underground or under-deck pipes and fittings, it is always best to call a professional and get their opinion.


No matter what is causing your pool to leak or where the leak is happening, it’s crucial to stop the leak as soon as possible.

Leaky pools cost more in water bills, are more difficult to keep clean and balanced, and require more maintenance. Ignoring a leak allows it to progress and worsen, which drives up the cost of eventual repairs.

Finding the leak in your pool is the first step to knowing what kind of repairs are necessary and will help you work with a pool professional or repair person to determine the right course of action more quickly.

Now you know how to find out if your pool is leaking and how to identify the source of the leak, so there’s no reason to not take action right away and save yourself additional time, money, and trouble in repairing a leaky pool.

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