Last Updated: February 28, 2021

How to Test for Pool Leaks

Written By: Pool Care Guide

When the presence of a leak isn’t obvious, we typically perform a Bucket Test to determine if there is a leak. Evaporation typically removes ½ of an inch, but as much as 1 inch of water each day. If you don’t notice your pool for a week, that can mean up to a drastic 7-inch drop in your water level. That can easily inspire the wrong assumption.

In this guide, we will start with a quick search around the easy-to-check points that commonly have issues with leaks. If we can’t find anything, we can move on to testing water levels to determine if there actually is a leak. If there is, we recommend that you click over to one of the leak-finding guides that we listed at the top of the page. They will take you to the guide applicable to your pool type.

Places to Quickly Check for Leaks

Okay, time for a quick inspection. Let’s do a quick and easy visual inspection. If there is a leak in an inground pool, it will most likely have developed at a mechanical point rather than within the pool wall. You should check around your filtration equipment to see if you can spot anything obvious. Here’s a quick list of filtration parts to check:

ChlorinatorFilterPool HeaterPool Pump

The Bucket Test 

(Inground and Aboveground Pools)

There is a simple test that you can perform that will answer a few important questions: Is the water loss due to evaporation, a leak in the pool, or a leak in the pool pump? Here’s what you are going to need:

  • Large Bucket (5-gallon)
  • Black Marker or Duct Tape

As was mentioned at the top of the page, water evaporation can remove up to an inch per day. We need to determine if the “leak” is causing the water to drop faster than evaporation. If it isn’t, then you probably don’t need to do anything. If the pool is losing more water than expected, you will do at least one more test.

Step 1: Turn off the Pool Pump

The pool pump is a potential leak source. Let’s turn it off for now. If there is a leak, this action will help us to gather a useful data point. Later, if a leak is determined, we will need to know if the leak is in the pool or the pool pump. “Step 5” goes into further detail.

Step 2: Turn off Auto-Refill Devices

These aren’t used in every pool. Turn yours off if you have one so that it will not interfere with the test.

Step 3: Place Bucket on Pool Step and Fill with Water

The bucket should be on the first or second pool step that is submerged in the pool water. Fill that bucket with water until the bucket’s water and the pool’s water are perfectly level. 

Step 4: Mark the Current Water Line on the Bucket

We don’t want to rely on your eyes and memory. Mark where the current water line is on the bucket. We will need to measure the difference between the water lines at the start and end of the test.

Step 4: Wait for Results (24 Hours)

Evaporation will reduce the bucket’s water level and the pool’s water level at the same rate. We need to eliminate the leak as a possibility. If there is a leak, the pool’s water level will lower faster than the bucket’s water level.

Pool Water Reduction: Evaporation + Potential Leak(s)

Bucket Water Reduction: Evaporation 

If There Is a Leak, Continue to Step 5

Step 5: Turn on the Water Pump

We can determine the source of the leak by comparing the rates that the water drains when the pool pump is “on” vs “off.”

When a leak is under pressure, the leak reduces the pool’s water faster.

When a pool pump is set to “on,” it increases the pressure within the pool pump. 

When we turn off the pool pump, the pressure within the pool pump is reduced. 

If turning on the pool pump increases the speed of the leak, that likely means that the leak is under increased pressure and located within the pool pump.

Step 6: Repeat the Test

Let’s repeat the test now that the water pump is set to “on.”

Step 7: Compare results from the first test to the second test

Did the water level drop faster with the water pump on? 

If yes, the leak is likely located in the water pump.

If no, the leak is likely in the pool.

Ink Test Method

What You’ll Need

Dark Ink (You can use phenol red test solution in the pH level testing kit)

Goggles

Throwaway Clothing

Step 1: Find the Rough Location of the Leak

This method is only useful if you have narrowed down the approximate location of the leak. If the ink is released too far away from the leak, the ink becomes useless. The reason for this is that ink dilutes rapidly when introduced to water. If it dilutes to the point that you can’t see it, you won’t be able to follow it to the source of the leak.

Finding the Horizontal Position

The location of the leak can be deduced by determining its vertical and horizontal position. The horizontal position should be easy enough. If the leak is significant enough to noticeably drain your pool’s water supply, it should leave a significant patch of wet ground wherever it is.

Finding the Vertical Position

If you know where the leak is on the horizontal plane, you are probably close enough to start performing the ink test. However, if you need to narrow it down more, just keep track of how quickly water is draining from your pool. When the drain on the water level significantly slows, you will know the near-exact height of the leak.

Inject Ink into the Water

If you have narrowed down the source of the leak, inject the ink as close to that source as possible. If you need to enter the pool to get close to the pool leak, move as slowly as possible. You don’t want to disturb the water. Movement creates turbulence that will disrupt the leak’s current. Without the current, there is no pull. If there is no pull, the ink will not head toward the source.

If you were correct in your estimation and careful in your application, the ink will head straight for the leak.

Conclusion

Okay, that’s it for now. Let us know if there are any burning questions that you have. We’ll be happy to tell you what we know and to research what we don’t. Have a great day and go enjoy your pool!

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