How to Tell if Your Pool Has a Leak
Is It Evaporation or a Leak?
Nothing worries pool owners faster than a dropping water level. Some water loss is completely normal, especially during hot weather, windy days, or heavy pool use. But if the water level is falling faster than expected, you may be dealing with a leak.
Leaks can happen in any type of pool — fiberglass, vinyl, concrete, or above-ground — and they can range from easy fixes to more serious plumbing issues. This guide explains the exact steps you can take to determine if your pool is leaking and how to narrow down the source.
Step 1: Understand Normal Evaporation
Before assuming the worst, start by understanding what normal water loss looks like.
Typical evaporation rates:
-
⅛–¼ inch per day in mild weather
-
¼–½ inch per day during hot, sunny, or windy weather
-
Higher loss if the pool is heated or uncovered at night
If you’re losing more than ½ inch per day, it’s worth testing for a leak.
Step 2: Perform the Bucket Test (The Most Reliable DIY Method)
The bucket test compares pool water loss to evaporation.
How to do it:
-
Fill a 5-gallon bucket with pool water to about ¾ full.
-
Place the bucket on the top step of your pool (partially submerged).
-
Mark the water level inside the bucket.
-
Mark the pool water level outside the bucket.
-
Leave the pump off for 24 hours.
-
Compare the two marks.
How to read results:
-
If both levels dropped equally → evaporation
-
If the pool level dropped more than the bucket → leak
This is the simplest and most accurate way to confirm a leak.
Step 3: Inspect the Equipment Area
Many leaks occur where the water is being pumped, filtered, and circulated.
Check the following:
-
Pump housing and lid O-ring
-
Filter tank and drain plug
-
Backwash line (common leak point)
-
Heater connections
-
Pipe unions and couplings
-
Chlorinator connections
Look for dripping water, rust stains, wet soil, or damp concrete. Even slow, small leaks can add up to major water loss.
Step 4: Check Around the Pool for Wet Spots
Walk around the pool perimeter and look for:
-
Spongy or soggy spots in the yard
-
Areas where grass is taller and greener
-
Damp mulch or softened soil
-
Cracks in concrete decking with moisture present
Underground plumbing leaks often show up as wet patches close to return lines or skimmer lines.
Step 5: Inspect the Skimmer and Return Fittings
Loose fittings are one of the most common causes of leaks, especially in fiberglass and vinyl pools.
What to check:
-
Cracks around the skimmer mouth
-
Separation between pool wall and skimmer box
-
Loose return jet fittings
-
Worn or missing gaskets
If the water stops dropping when it hits the bottom of the skimmer opening, the leak is likely in the skimmer line or skimmer throat.
Step 6: Examine the Pool Liner or Shell
Leaks can also occur directly from the structure of the pool.
For fiberglass pools:
-
Look for cracks, spider cracks, or damage around steps and fittings
-
Inspect seams where different pieces meet
-
Check lights and return cutouts for separation
For vinyl liner pools:
-
Look for tears, punctures, or stretched liner areas
-
Check around ladders, lights, and corners
-
Feel for soft spots behind the liner (water behind liner)
If the water stops dropping at a particular level, the leak is likely near that height.
Step 7: Dye Test Suspected Leak Areas
A dye test helps confirm leaks in specific locations.
How to do it:
-
Turn off the pump to stop water movement.
-
Use leak detection dye, food coloring, or milk.
-
Squirt a small amount near:
-
Steps
-
Skimmer
-
Returns
-
Light niches
-
Visible cracks
-
-
Watch whether the dye gets pulled into the area.
If the dye moves toward a crack or fitting → that’s the leak.
Step 8: Check Underground Plumbing Lines (If Needed)
If you suspect a plumbing leak, the bucket test + water level behavior helps narrow it down.
Possible signs of an underground leak:
-
Water loss only when pump is ON → pressure-side leak
-
Water loss only when pump is OFF → suction-side leak
-
Water loss regardless of pump → structural leak
These leaks require professional pressure testing and should not be ignored.
Common Signs Your Pool Has a Leak
-
Losing more than ½ inch of water per day
-
Air bubbles coming from return jets
-
Pool pump struggling to prime
-
Visible cracks or gaps
-
Wet spots around the pool
-
Higher water bills (if auto-fill is used)
-
Sinking or shifting pool decking
-
Dirt or sand appearing in pool (suction-side leak)
Common Causes of Pool Leaks
-
Worn or cracked skimmer throat
-
Loose or damaged return jets
-
Underground plumbing leaks
-
Liner tears or punctures
-
Failed gaskets or seals
-
Cracked fiberglass shell
-
Damaged light niches
-
Filter or pump leaks
When to Call a Professional
Some leaks are simple DIY fixes, but others require specialized testing.
Call a professional if:
-
You lose more than 1 inch of water a day
-
The bucket test confirms a leak
-
You see structural cracks
-
You suspect underground plumbing issues
-
You cannot locate the leak after checking the basics
Leak detection often requires:
-
Pressure testing plumbing lines
-
Dye detection inside fittings
-
Electronic listening equipment
-
Structural inspection
Conclusion: Catch Leaks Early to Protect Your Pool
A small leak can become a big problem — from erosion around the pool to equipment failure or major water damage. Using the steps in this guide, you can quickly determine whether your pool has a leak and narrow down the source.
If you need help diagnosing or repairing a pool leak, the experts at Mock Pools & Ponds are here to help. We serve homeowners throughout Canton, Akron, and Northeast Ohio with professional leak detection, equipment repair, and year-round pool care.
how to find pool leak, pool losing water, pool evaporation vs leak, pool leak detection, how to find pool leak, pool losing water, pool evaporation vs leak, does my pool have a leak