The best way to tell if your pool is leaking or evaporating is to perform a bucket test. Fill a bucket with pool water, place it on a pool step, mark both water levels, turn off the autofill, and compare after 24 hours. If the pool drops more than the bucket, the pool may have a leak.
The bucket test does not locate the leak. It only helps confirm whether the pool is losing more water than evaporation. A professional inspection is needed to find the actual source.
Evaporation vs. Leak -- The Core Difference
Both evaporation and leaks cause the pool level to drop. Both can look identical to the naked eye -- the pool is low, you add water, the cycle repeats. The difference is the mechanism.
Water leaves the pool surface and turns into vapor. Affected by heat, sun, wind, humidity, water temperature, water features, and splash-out. Both the pool and a bucket of water exposed to the same conditions will drop at similar rates.
Water escapes through a physical opening -- a skimmer, light conduit, return fitting, main drain, underground pipe, structural crack, or equipment failure. The pool drops faster than a bucket of water exposed to the same conditions.
Evaporation is normal. A leak is not. But both can look like routine water loss until you measure. At Leak and Subsurface Locators, LLC, the first question on every call is not "where is the leak?" -- it is "how much water is actually being lost, and is that more than evaporation?"
Warning Signs That Suggest a Leak
These signs do not prove a leak exists -- and they do not locate one. They are clues that tell you testing is warranted.
How to Do the Bucket Test
Fill the pool to its normal operating water level.
Turn off the autofill completely. If it runs during the test, it replaces lost water and produces a false result.
Fill a clean 5-gallon bucket with pool water. Place it on a pool step so it is partially submerged -- not on the hot deck.
Mark the water level inside the bucket with tape or marker. Mark the pool water level at a fixed point on the pool wall or outside the bucket.
Wait 24 hours. Do not swim, run water features, or allow splash-out. Do not move the bucket.
Compare the two levels. If the pool dropped significantly more than the bucket, the pool may have a leak. If both dropped about the same, evaporation may explain the loss.
Do not test during rain, heavy wind, or while water features are running. These conditions skew the results. If conditions were poor, repeat the test on a calmer day for an accurate comparison.
Pump-On vs. Pump-Off -- A Useful Clue
Watching how water loss changes with the pump running versus off can help narrow the investigation before a professional inspection begins.
May suggest the leak is structural -- a crack, skimmer separation, light conduit, or static leak point that loses water whether or not the system is running.
The pool is losing water even without pressure in the lines.
May suggest a pressure-side plumbing issue -- a return line, fitting, equipment leak, or underground pipe that leaks more when the system is under pressure.
Water features running with the pump can also increase apparent loss.
Pump-on vs. pump-off differences are clues -- not diagnoses. A professional inspection with pressure testing and dye testing is still needed to confirm the actual source.
What the Bucket Test Can and Cannot Tell You
- Whether the pool is losing more water than evaporation
- Approximate daily water loss rate
- Whether a professional inspection is warranted
- Whether loss is consistent day to day
- Where the leak is located
- Which component is failing
- Whether the leak is structural or plumbing
- Whether more than one leak exists
Free Tools to Help You Evaluate Water Loss
These free tools help you measure and evaluate your pool's water loss more precisely -- so you can communicate clearly with a professional or determine whether an inspection is needed.
Common Mistakes When Evaluating Water Loss
LBA Resources
Jeff David's Perspective
At Leak and Subsurface Locators, LLC, the first thing we establish on every call is how much water the pool is actually losing -- and whether that loss changes with the pump on or off. Most homeowners have not measured it. They are guessing.
The bucket test is not complicated. But it has to be done correctly -- autofill off, no swimming, bucket in the pool not on the deck. When it is done right, it gives us a real data point to work from before we ever arrive on site. That saves time and helps the customer understand what they are actually dealing with before the inspection begins.
-- Jeff David, Founder | Leak Business Academy, LLC | Leak and Subsurface Locators, LLC
Measure First -- Then Decide Whether to Call a Professional
To know if your pool is leaking or just evaporating, perform the bucket test. If the pool drops significantly more than the bucket over 24 hours with no swimming and the autofill off, the pool may have a leak. Observe whether the loss changes with the pump on or off -- this can help narrow the investigation before calling a professional.
Use the free Leak Business Academy tools to evaluate your water loss. If the bucket test suggests a leak, a professional inspection is needed to find the actual source -- the bucket test cannot tell you where the water is going.
Measure Your Water Loss Before Guessing
Use the free Leak Business Academy tools to evaluate whether your pool's water loss is normal evaporation or something that needs professional attention.