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You come home and look outside only to notice that your water level keeps dropping. You’re not sure if it has a leak since it can be tough with the sheer size of the pool but want to make sure. Here are a few pool contractor tips to help you determine whether it is water loss or a leak.

Since not all water loss is a leak, we need to eliminate the obvious culprits:

Splash out: Splash out naturally occurs when swimmers are entering and leaving the pool. It can also be caused by water features such as spillways or waterfalls. It may seem negligible but it can add up over the course of a day with several swimmers.

Wind: Surprising right? Depending on your landscaping and location, this can become a huge problem for pools that do not have automatic covers. Windy conditions change the surface area of the pool water and increase heat loss as well as evaporation.

Relative Humidity: When the air is humid, the ability for air to take on more water is decreased since it is already saturated. Low humidity coupled with high temperatures/sun exposure can lead to excessive evaporation.

Backwash: If you have a filtration system that uses a backwash feature, this can increase the rate that you have to fill your pool. The multi-port valve could be leaking water out of the backwash line, so be sure to check this first.

Evaporation: This is a tough one due to a large number of variables that can cause it. The general rule is anything over a 1/2” of water loss in a day needs to be investigated. There is a useful tool that is called the bucket test that can be used to determine if it is evaporation or a leak. To keep evaporation to a minimum the air & water temperatures should have a difference of 2-4 degrees maximum.


The bucket test is an excellent tool to determine if water loss is due to evaporation or an actual leak.

  • Fill your pool to its normal level and turn off your autofill. Make sure not to add any more water.

  • Take a bucket and fill 3/4 of the way and mark the top water line inside the bucket

  • Place the bucket on your first or second step in your pool. You will need about 6 inches of the bucket to be below water. Mark the water level outside the bucket.

  • Wait 24 hours **THIS IS IMPORTANT**

If the water marker outside the bucket is lower than the marker inside the bucket, you most likely have a leak. You will need to measure between the waterline and marker. They should both be the same distance or at least very close. You should lose about 1/4″ to 1/2″ of water to evaporation. If it rains, the test will have to be redone.

Some DIY – Eliminating the obvious variables:

We want to make sure we eliminate as many of these variables as possible before we proceed with costly diagnostics. First, we will want to mark the water level. You can use some duct tape and put it right at the waterline. Make sure to put the time and date on it so we can determine the interval. 

Make sure that:

  • No one is using the pool to avoid splash out. If you have an automatic cover, close it to cut down on evaporation as well as potential water loss from wind if applicable.

  • If possible, perform test on days when you have good humidity if you don’t have an automatic cover.

  • Use the bucket test to help eliminate evaporation as the culprit.

  • Do not backwash your system during this waiting period.

  • Turn off your auto-fill and/or do not hose fill the pool.

After 24 hours, check the duct tape and measure from the bottom of the piece of tape to the waterline. If it measures below 1/2”, you are probably not losing water and can be attributed to environmental factors. If it’s more than 1/2”, then you need to set-up a service call to proceed with leak diagnostics to determine the source.

Clues on where your pool is leaking: 

To help expedite the diagnostics, here are some clues that can help determine where the leak is coming from.

  • Does the pool lose water when the pumps are on or off? This can indicate a structural problem rather than a plumbing problem.

  • Where does the water stabilize? If it’s right by a light niche or skimmer housing, these can often be the source of the leak.

  • Are there any wet spots at the equipment pad or in the yard? A quick visual check can verify if the equipment is causing a leak. If you find swampy areas in your yard, that can indicate a leak underground.

  • If the plumbing is suspected, narrow it down to which pump by only using one at a time. This will help determine which part of your plumbing system is causing the leak.

  • If you have a spa, run it for 30 minutes and see if it is losing water by marking the water level before and after. This will help eliminate the spa as a possible culprit. (Note: Only do this if the pool and the spa share the same equipment.

​Contact Quantus Pools for Leak Detection and Repair


If your inground pool is experiencing water loss contact Quantus Pools today. We offer comprehensive pool repair services and pool maintenance services throughout the greater Chicago area. Our technicians are experts at diagnosing and repairing leaks.




Schedule a Service Call

Our professionals will make your life easier and make sure your pool is in perfect condition.

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