DIY Pool Repair

How To Find Swimming Pool Leaks

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• Home
  Swimming Pool Leak Detection
• Pool Resources
  List of swimming pool resources - Must read for any pool owner
• Signs of damage
  Obvious deficiencies can be a significant possibility for water loss
• Water loss characteristics
  Has the leak developed slowly over time or suddenly over a short period of time
• Pool plumbing systems
  Understanding your plumbing system is critical in being able to diagnose a leak in your swimming pool
• Hydrostatic test
  Learn how to monitor water loss and conduct a hydrostatic test for your pool
• Test Analysis
  Analyze the data from this leak detection test to find out where your pool is leaking
• Condition 1
  Leaking the same with plumbing system on and off
• Condition 2
  Leaking more when plumbing system is on, but water loss in both conditions
• Condition 3
  Leaking more when plumbing system is off, but water loss in both conditions
• Condition 4
  Leaking when plumbing system is on, not leaking when it is off
• Condition 5
  Leaking when plumbing system is off, but not leaking when it is on
• Leak detection test 2
  Another easy method to determine where your pool is leaking
• Water Level Test conclusions
  Analyze the results of the water level leak detection test
• Faceplates & Gaskets
  water level holds anywhere where gaskets or faceplates are touching the waterline
• Skimmer & Mid Wall
  water level below skimmer mouth but above return outlets
• Return Outlets
  water level holds at the height of wall returns
• Indefinite Drop
  water level continues to drain down past wall returns or lower
• Leak Detection Dye Test
  Use colored dye to locate leaks in your swimming pool
• Common Pool Leak Points
  Breakdown of pool components prone to failure and associated water loss symptoms
• Hole In the Liner
  See symptoms associated with a hole in the liner of your swimming pool
• HRV Failure
  Hydrostatic relief valve failure symptoms
• Filter Head Gasket
  Filter head gasket alignment is a common location for unexplained water loss
• Leaking Skimmer
  See symptoms associated with a leaking or cracked skimmer
• Leaking Return Lines
  See symptoms associated with leaks in the swimming pool return lines

Leak Test Condition 4

Leak condition 4 refers to the pool leaking when the plumbing system is on, and not leaking when the plumbing system is off

Pool Leaks When Pump Is On

The leaking condition where the pool leaks when the pump is running but seems to hold water well enough if your turn off the pump off is either going to be related to a problem with your filter, or more likely a leak in one or more of the return lines going to the pool.

Symptoms Of Return Line Leaks

One of the most tell tale sign of a long term return line leak is to see sinking, cracking or uneven ground surfaces and especially right overtop of where each return fitting meets the pool wall.

Often times you will see that one or more of the return lines in your pool has been repaired at the pool wall evidenced by a patched area over the return fittings. If there are any returns that have not been dug up previously this would be highly suspect if one or more have been repaired. Service professionals often prefer to repair all return fittings if one is found to be faulty given the high likelihood for failure of the others. If you already have the tools on site to dig up one return line then it is more efficient to do the others also.

Likely Leak Locations

Based upon the leak characteristics displayed by your swimming pool during the hydrostatic leak test, here is a list of the more likely areas of concern for your pool. This information is not sufficient for stand alone diagnosis of your swimming pool leak in most cases, but can very often lead to an efficient diagnosis and repair due to recurring instances of these common pool failures:



(small leak of less than 1” / 2.5cm per day)
-Small crack or loose fitting on return line
-Leak in the pump, filter or heater
-Filter head gasket out of alignment

(medium leak of 1-3” / 2.5-7.5cm per day)
-Broken return line
-Filter head gasket out of alignment

(large leak of more than 3” / 7.5cm per day)
-Multiple return line leaks
-Filter head gasket out of alignment
-Broken fitting or pipe in return line


If you suspect that you have one of the leaks here, or you have a pool leak that meets condition 4 of the hydrostatic leak test then you should read what industry experts say about a pool leaking when pump is running or you can choose to proceed to the next leak test which is the water level leak test



The menu on the right is a chronological step by step process to determine where a swimming pool is leaking. This website is written as a readthrough technical assistance guide for locating leaks. When you believe you have identified where the pool is leaking you need to go to our sister website to see pictures and learn more about the actual swimming pool leak repair process.