Swimming Pool Leak Detection Basics – Finding the Leak in my Pool

backyard pool inspection raleigh

All quotes are based on the size, depth and features of your individual pool so please be ready with the following information:

  • Current pictures to text and/or email
  • Type of construction - plaster/concrete/gunite/shotcrete or fiberglass or vinyl
  • Type of pool - pool only or pool/spa combo with spillover spa
  • Pool Dimensions – length, width, shallow depth, deep-end depth
  • Features – infinity edge, waterfall, sheer decent, deck jets, etc.
  • If vinyl pool – what type of stairs: plastic or vinyl liner
  • How much do you believe the pool is leaking per day?
  • When did you first notice the leak?
  • If you don’t add water where does the water stop (take pictures)?
  • Does the pool leak more (or only) with the filter pump running?
  • Does the pool leak more (or only) with a water feature running?

The water in the pool or feature MUST be clear and MUST be filled to the normal operating level upon our arrival for us to perform the leak test and detection.

How much water loss is normal evaporation?


Unfortunately, there is no magic number or standard formula to determine evaporation loss. Evaporation can range from 1/8” to 1/2” per day. There are many variables that effect evaporation such as water features and weather. Water features such as: spa spillovers, infinity edges, sheer descents, bubblers, deck jets/laminar jets will ALL significantly increase water loss. Evaporation caused by weather is most significant in the fall when we have sunny warm-hot days and cool nights with low humidity Evaporation increases with:

  • increased sun exposure
  • increased wind
  • lower humidity
  • If water temperature is higher than the air temperature

Evaporation is not affected by the depth of the pool, it is affected by the surface area (length x width for rectangular shape pools). Keep in mind, that in North Carolina, if you do not add water to the pool, it will completely evaporate within 1 year.

A simple, inexpensive test you can perform to determine if your pool is leaking:


The “Bucket Test” allows you to check the evaporation rate compared to possible water loss. Here is how the test is performed:

  • Begin with the pool or water feature at its normal level
  • Turn off or disable any auto-fill
  • Fill a 5-gallon bucket with water to within 1 to 3 inches of the top.
  • Place the bucket in the pool and on the first step. (You will need to use a few bricks or stones to weigh the bucket down so it will not float in the water.)
  • Mark the level of the water inside the bucket, using a grease pen or piece of tape
  • Mark the level of the pool or spa on the outside of the bucket.
  • Best is to use a translucent bucket and match the water level in the bucket with the water level in the pool.
  • After a day or 2, mark the new levels, inside and outside.
  • If the pool and bucket level differ more than 1/4", you may have a leak.

Leaks can be expensive

In addition to the cost of the water, there are additional chemical costs. Some municipalities in North Carolina, such as OASA in Chapel Hill/Orange County frequently fine homeowner’s for “excessive water use”. If you are adding water via city water or community water in North Carolina, the water companies add phosphates to reduce metal buildup in the supply and sewage pipes. These phosphates need to be removed from pool water as they will promote algae growth, therefore increasing chlorine demand. If you are adding city water or community water or well water it has algae and metal contaminants that also need to be addressed. Regardless of where these conditioning chemicals/products are purchased, they are NOT cheap. If you do not have an autofill and are not constantly on top of refilling your pool, the water level can easily drop below the skimmers and pumps and plumbing will most likely be damaged from the pumps overheating. Almost ALL pool maintenance contracts defer maintaining the water level to the homeowner and are NOT liable for pump and/or plumbing damage caused by low water levels. If you have a pool maintenance contract with chemicals included; almost ALL agreements have a clause to charge for chemicals due to excessive water loss. Excessive water loss is easy for the pool maintenance company to identify, especially if you have a salt system. Below is a simple chart of how water loss adds up annually: 1/2” Per Day Leak Pool Size Surface Area Gallons per Day Gallons per year 14 X 28 392 sqft 122 44,530 15 X 30 450 sqft 140 51,100 16 X 32 512 sqft 160 58,400 18 X 36 648 sqft 202 73,730 20 X 40 800 sqft 250 91,250 40 X 75 3000 sqft 935 341,275. Bottom line is that it is much less expensive to pay for the leak detection and repair than the continued burden of cost of the leak.

Why do Swimming Pools leak?

There are many reasons why pools leak:

Newer Pools

  • Your pool may have leaked from the day it was built.
  • During construction a pipe fitting may not have been glued properly.
  • On occasion heavy equipment is used during the final grading of pool decking leaving light conduits and plumbing as targets to get run over and cracked.
  • Even though all of your pool plumbing will be inspected under pressure during new construction, small leaks can still sneak by which can become larger over time.

Older Pools

  • A small leak in plumbing/pipes will cause tree and plant roots to migrate toward the moisture in the soil. These roots will wrap around pool plumbing and crack a pipe.
  • Ground settling issues can cause plumbing to sag and break at the pool wall.
  • Small leaks always create a larger problem eventually.
  • Pool tile and grout can crack below the normal water line, or the pool may just develop a crack through the shell.
  • Any place that plastic pipe (PVC) comes through the pool shell, (main drains, return lines etc) can develop leaks as the pools interior finish begins to deteriorate.
  • As weather changes your pool will expand and contract generally making small leaks bigger leaks.

Common Backyard Pool Leaks

  • Equipment pad leaks – If you have an sand filter with a multiport/diverter valve the internal gasket wears and deteriorates over time and the water leaks out the backwash line. Look for water dripping or streaming from equipment. Is there water on your equipment pad
  • Pool Light conduits – Frequently the electrical conduits to the lights are not properly glued and will leak
  • Skimmers – When pools settle sometimes there will be hairline cracks at the point the skimmer body/throat meets the pool shell
  • Channel Drains – are long and rectangular and frequently develop hairline cracks along one or more edges