Pool Losing Water? How to Know If It’s a Leak or Evaporation

Allie Ogletree
Written by Allie Ogletree
Updated September 28, 2022
A swimming pool from a low angle view
Photo: Marcus Chung / E+ / Getty Images


  • Pools can lose water from evaporation or a leak.

  • Signs of a leak include excessive moisture and chemical imbalances.

  • You can test and find leaks with bucket and dye tests.

  • If you can’t pinpoint the location of the leak, call a pro.

Get quotes from up to 3 pros!
Enter a zip below and get matched to top-rated pros near you.

Pools are a fun way to cool off on hot days, but noticing that your pool is losing water can raise serious concerns. Typically, pools lose water for one of two reasons: evaporation or a leak. Evaporation naturally occurs in any body of water, but it may increase under certain conditions, such as hot, humid weather. Leaks, however, indicate a bigger problem that a professional may need to address. 

Read on to learn whether your pool is naturally evaporating or has a leak that needs fixing.

What Causes Pool Leaks?

Although pools are constructed to be watertight, several issues can cause leaks. For instance, seals can deteriorate, especially if you aren't performing regular pool maintenance. Additionally, if your pool's plumbing fittings or accessories, like light fixtures, stop working as intended, leaks can occur. 

It's essential to find leaks early so you don’t lose money on wasted water, heat, and chemicals. You’ll want to patch your pool liner as soon as possible if that’s the issue to ensure things don’t get any worse.

But it's also critical to detect them to preserve your pool's overall structure. Leaks left unaddressed can wash away your pool's fill dirt and cause other costly problems.

Common Causes of Pool Evaporation

All bodies of water experience evaporation, but some conditions cause it to increase. For example, high temperatures, lots of humidity, and high winds can increase your pool's evaporation rate. Pools without enclosures or tree cover will also evaporate faster than those with shade and protection because they are more exposed to the weather elements. 

Because the weather affects evaporation so much, you're likely to see much more evaporation during warmer seasons than you would during the cooler months. If you notice your pool losing more water than usual during cooler months, you may have a leak.

How Much Pool Water Loss Is Normal?

Pools in perfect working order will naturally lose water over time. It's typical for residential pools without a cover to lose up to a quarter-inch of water per day during the summer. Adding things like an enclosure and a pool cover can help slow down evaporation. Heated pools and pools with water features, like fountains, may also evaporate faster than pools without these components.

Water Evaporation Chart

The amount of water that evaporates from your pool depends on the temperature of the water, the air temperature, how humid it is, and the velocity of the air that passes above the water’s surface. However, you can still get a rough idea of average evaporation losses to determine if your pool is losing water at an above-average rate.

Below is a general water evaporation chart per season based on minimal activity. These estimates are for a 400-square-foot pool located in an arid location. If more people use your pool and make a splash, you’ll find the water rate can increase by as much as twice these rates.

SeasonInches Lost (per Month)Gallons Lost (per Month)

For information on evaporation rates in your area, check with your state or local government for evaporation data to help you compare your pool’s evaporation rates to the average in your region. 

How to Identify a Pool Leak

Nothing’s better than lounging in your pool on a hot day. Don’t let a leak put a damper on your fun in the sun. Learn how to identify leaks before they can turn into a huge problem (and mess).

Water loss is just one sign of a leak in your pool. Several other signs that indicate your pool may have a leak include:

1. Excessive Moisture

Look for any wet or mushy spots in the grass between your pool and its equipment pad. 

2. Cracked Concrete or Tiles

Leaks that occur below the surface can shift the ground your pool sits on, causing cracks. Therefore, cracks in your pool's concrete or tiles could mean there’s an underground leak. 

3. Chemical Imbalances

When water drains from a leak, your pool's chemicals drain with it. Inconsistent chemical levels can be a major red flag. As you’re cleaning your pool and performing maintenance, keep a close eye on your chemical levels and be on the lookout for changes in your usual chemical balances.

Typical levels for pool chemicals are as follows:

  • pH levels: 7.2–7.8

  • Total alkalinity: 80–120 ppm

  • Salt: 2,700–3,400 ppm

  • Cyanuric acid: 30–50 ppm

  • Calcium hardness: 200–400 ppm

How to Test Your Pool for Leaks

A swimming pool in a backyard of a house
Photo: DigiStu/iStock / Getty Images Plus / Getty Images

If you suspect your pool is losing more water than it should, you can run a simple test to determine whether it's leaking.

The Bucket Test

This test will help you determine whether your pool is evaporating as it usually would or whether it has a leak. Make sure no people or animals use the pool during the test, or it will skew the results. Additionally, if it rains during the test, you'll need to start over on another day. 

  1. Fill your pool to its normal water level. 

  2. Add some of your pool water to a bucket, filling it to about 1 inch from the top.

  3. Place the bucket on the first or second step of your pool so that it's submerged about 5–6 inches into the water.

  4. Use a marker or pen to mark where the water stops both inside and outside of the bucket.

  5. Wait 24 hours.

  6. Check the water levels inside and outside of the bucket.

If the water outside of the bucket dropped more than it did inside of the bucket, then you likely have a leak.

How to Find the Location of the Leak

If you're fairly sure your pool is leaking, then the next step is to find the origin, so you can get back to enjoying your pool ASAP. 

As effective as the bucket test is at helping you identify whether or not your pool has a leak, it won’t help you identify where the leak originated. To find the source of your pool leak, you’ll need to perform a more in-depth test called the dye test.

The Dye Test

Perform this test on a day with low wind, and turn off your pool's filtration system so the water is as still as possible. 

For the test, you'll need:

  • Leak-finder dye or dark food coloring

  • Goggles

  • A snorkel

Follow these steps for the dye test: 

  1. Fill your pool to its normal water level.

  2. Go to where you suspect a leak is occurring.

  3. Add a few drops of dye or food coloring.

  4. Observe where the dye flows.

  5. The dye or food coloring will naturally flow toward your leak. If you have a leak at the bottom of your pool, you'll likely need some goggles and a snorkel so you can effectively follow the dye's path. 

Once you determine the leak's location, you can attempt to fix it yourself or call a local pool service to help you. 

If this test doesn't lead you to the leak, your underground plumbing may be the culprit. If this is the case, you may want to call a professional to identify the leak's location so you don’t inadvertently damage your pool's plumbing.

Common Pool Leak Locations

You may locate a pool leak in any part of your pool that holds water, but a few areas are more likely to be the issue than others. Here are some of the most common pool leak locations.

Pool Skimmer

This is the first place you should look for a leak. If your skimmer materials are damaged or worn over time, the area where the skimmer attaches to the pool can start to leak. You should also check around the piping exiting the skimmer to see if any leaks have developed.

Return Piping

While leaks can be common in your pool’s return piping, the pipes themselves can be hard to access if they’re buried underground. Instead, you can check the ground around your pool for soft, wet areas that may have formed because of an underground leak.

Main Drain

A main drain leak is one of the toughest pool leaks to spot due to the drain’s location at the bottom of the deepest part of the pool. You may want to contact your pool builder or service company about getting access.

Pool Lights and Jets

Any openings in the structure of your pool can be prone to leaks. This includes the watertight seal around your pool lights or jets, which can wear down over time. Your pool service company can help you to reseal the areas around these fixtures.

Pool Structure

Structural leaks vary in how easy they are to spot. Some are as obvious as cracks in the surface or tiling of your pool, while others are so subtle they require the dye test to locate. If your pool’s structure is aging, it may be time to call a pool renovation company for repairs or resurfacing.

Tips for Handling a Pool Leak

If you think your pool is losing water because of a leak, you’ll want to take a few basic steps to properly identify the problem. Some of the best steps you can take include the following:

  1. Turn off your pool pump and auto-fill system if you have one.

  2. Look for common leakage signs like excessive moisture, cracks, or chemical imbalances.

  3. Run the bucket test to determine if your pool is actually leaking.

  4. Run the dye test to find the origin of the leak.

  5. Attempt to fix the leak yourself or call a pro, depending on the situation.

When to Call a Pro

It’s normal to lose an inch or less of water to evaporation in a typical week. However, if your bucket test results point to a leak, it’s a good idea to call in a pool professional. A certified pool technician can help you find out exactly why your pool is losing water and locate the exact source of the leak to make repairs.

It’s important to address pool leaks promptly to prevent them from growing and causing more expensive damage down the line. Investing in routine maintenance and repairs will save you time and money in the long run.

Frequently Asked Questions

Your pool should only lose around 1/4 of an inch of water per day, give or take. More wind, sunlight, and heat will cause this number to increase, while rainy or cloudy days will decrease the amount of water that evaporates.

Need professional help with your project?
Get quotes from top-rated pros.