A leaking swimming pool isn’t just a nuisance — it can lead to structural damage, rising water bills, equipment failures, and algae growth. The longer it goes unnoticed, the more costly the repairs can become. Fortunately, there are several telltale signs that homeowners can observe without needing professional tools or expertise.
In this article, we’ll cover the top five most common signs that your in-ground pool may have a leak. Each section will guide you through the reasons behind it, what to look for, and how to verify it, enabling you to catch problems early before they escalate.
1. Rapid Water Loss Beyond Normal Evaporation
One of the most apparent signs of a leak is losing more water than expected. While all pools lose water from evaporation — especially during hot, dry, or windy weather — a drop of more than 1/8 to 1/4 inch per day should raise a red flag.
Why it happens:
Leaks allow water to escape the pool shell or plumbing system and seep into the surrounding ground. Depending on the location of the leak, this water loss can occur whether the pool pump is on or off. In many cases, the pool will stop losing water at a certain level, indicating the leak is at or near that point.
What to look for:
A water level that drops significantly overnight
The need to refill your pool more than once per week
The autofill system runs constantly.
A sudden spike in your water bill
How to verify:
Perform the bucket test:
- Fill a bucket with pool water and place it on a step in the pool.
- Mark the water level on both the inside and outside of the bucket.
- Wait 24 hours without using the pool.
- Compare the two water levels — if the pool water level drops more than the water inside the bucket, your pool is likely leaking.
Additionally, if the pool appears to lose more water while the pump is running, the leak may be located on the pressure side of the plumbing. If it leaks more when the pump is off, it could be due to issues on the suction side or from the pool structure itself.
2. Wet Spots or Soggy Ground Around the Pool
Another strong indicator of a leak is the presence of excess moisture in the ground around the pool. If you notice consistently wet soil, puddles that won’t dry, or unusually lush grass near your pool or plumbing lines, your pool might be leaking underground.
Why it happens:
Leaks from plumbing lines or structural breaches can release water into the surrounding soil, potentially causing damage. Over time, this can lead to erosion, uneven settlement, and even the formation of sinkholes.
What to look for:
Muddy, soft, or spongy spots in the yard
Pool deck lifting or sinking in certain areas
Isolated patches of bright green grass
Puddles forming near the equipment pad or plumbing lines
How to verify:
Walk the perimeter of your pool and feel for soft or sunken areas.
Dig a small test hole in the suspected area. If it quickly fills with water, you likely have an underground leak.
Turn off irrigation to rule out sprinkler leaks.
Smell the water in damp spots. If it smells like chlorine, it’s probably pool water.
Leaks in underground return lines, skimmer lines, or main drain lines are common culprits. These often require pressure testing and professional leak detection equipment to confirm and repair.
3. Cracks, Falling Tiles, or Shifting Decking
Visible damage to your pool’s structure is another red flag. While not every crack means a leak, any new or worsening structural issues should be carefully examined.
Why it happens:
As water leaks into the soil beneath the pool, it can cause soil erosion and settlement. Over time, the loss of support causes parts of the pool shell or decking to crack, shift, or collapse.
What to look for:
Cracks in the pool floor, walls, or tile line
Loose or falling tiles or coping stones
Gaps between the pool and the surrounding deck
Pool deck sections that have lifted or sunk
Visible voids or depressions in landscaping near the pool
How to verify:
Make a mental note of any cracks you see and check for growth over time.
Use a dye test: squirt a bit of pool dye or food coloring near a crack with the pump off. If it’s drawn into the crack, it’s likely a leak.
Watch for moisture stains, calcium buildup, or algae growth around cracks — these can indicate that water is escaping through them.
Cracks can exist in concrete, fiberglass, or vinyl liner pools, though they manifest differently. Gunite pools may exhibit hairline fractures or more severe structural cracks. Fiberglass pools might display bulging or spider cracks. Vinyl liners can tear or pull away from fittings, allowing water to seep behind the liner.
4. Trouble Maintaining Chemical Balance
If your pool chemicals seem to disappear faster than usual — or you’re fighting constant algae or cloudy water despite regular maintenance — a leak may be to blame.
Why it happens:
When your pool leaks, you lose chemically treated water, which is replaced by untreated tap water (via autofill or manual refilling). This creates a constant cycle of dilution, disrupting chlorine levels, pH, alkalinity, and other critical chemical balances.
What to look for:
Needing to add chlorine, salt, acid, or stabilizer more frequently
Rapid drops in chlorine levels, even after shocking the pool
Constant algae growth, especially in the same areas
Cloudy water despite filtration and proper chemical application
How to verify:
Check for falling CYA (stabilizer) or salt levels without doing a water change.
Perform a 24-hour chemical loss test: balance the pool, don’t add chemicals, and test again the next day. A significant drop in chlorine or other chemicals indicates dilution.
Combine this with the bucket test to rule out evaporation.
Algae and water cloudiness are symptoms, not the root cause. If you’re constantly treating these issues, especially alongside other leak symptoms, a hidden leak may be undermining your water chemistry.
5. Air Bubbles in the Return Jets or Pump Losing Prime
If you notice air bubbles blowing from your return jets or your pump struggles to pull water (known as losing prime), this can be a sign of a suction-side plumbing leak.
Why it happens:
Suction-side leaks typically occur before the pump, often in the skimmer line, main drain line, or pump fittings. These areas are under vacuum when the pump runs, so even a small crack can draw in air, which then circulates through the system.
What to look for:
A stream of bubbles constantly coming out of the return jets
Gurgling sounds in the skimmer or pump
A pump strainer basket that’s full of air instead of water
The pump losing prime or not starting properly
Visible air leaks at the pump lid or pipe unions
How to verify:
Check that the pool water level is mid-skimmer or higher (low water can cause air entry).
Inspect and lubricate the pump lid O-ring — if damaged, it can allow air in.
Perform a shaving cream test on the suction-side plumbing joints while the pump is running. If there’s a leak, the shaving cream will get sucked in.
Observe when the air appears — if bubbles only appear when the pump is on, it suggests a suction leak. If the pump loses water when turned off, it might be draining backward through the leak.
While these leaks don’t always result in apparent water loss, they hinder circulation, wear out your pump, and often coexist with water leaks. Many homeowners notice air bubbles long before they realize they leak.
What to Do if You See One or More Signs
If you’ve identified one or more of the signs above, don’t ignore them. Pool leaks only get worse with time, leading to the following:
Higher utility bills
Chemical and water waste
Equipment strain or failure
Soil erosion and structural damage
Here’s what you should do next:
- Perform simple verification tests, such as the bucket test or dye test.
- Rule out non-leak causes (splash-out, evaporation, improper maintenance).
- Observe patterns: When does the leak occur? Is it worse when the pump runs? Does the water stop dropping at a certain level?
- Document what you find — photos, measurements, dates.
- Call a professional if you suspect a structural or underground plumbing leak.
Why Choose Precision Leak Detection
If you’re located in Palm Beach County and suspect your pool is leaking, trust the experts at Precision Leak Detection to find and fix the issue efficiently.
With over a decade of hands-on experience and thousands of successful leak detections to its name, Precision Leak Detection combines professional-grade equipment with real-world expertise to identify even the most elusive leaks. From pressure testing plumbing lines to performing underwater dye inspections and electronic listening, we leave no stone unturned.
Whether you live in Boynton Beach, Boca Raton, Belle Glade, Lantana, Tequesta, or anywhere else in Palm Beach County, Precision Leak Detection is ready to help you protect your investment and restore your pool’s performance.
Don’t let a small leak turn into a big problem — call today for professional diagnosis and repair.
