The Most Common Causes of Pool Leaks (2026)

Swimming pools naturally lose some water due to evaporation, but excessive water loss is often a sign of a pool leak.

Every year, homeowners throughout New Jersey contact us because they’re adding water more frequently, noticing wet spots around the pool, or struggling to determine whether they’re dealing with evaporation or an actual leak.

The challenge is that pool leaks can occur in many different locations. Some are easy to spot, while others remain hidden underground or behind pool structures.

Understanding the most common causes of pool leaks can help you identify potential problems early and avoid unnecessary repairs.

If you’re unsure whether your pool is leaking, start by reviewing our guide on determining whether you’re dealing with a pool leak or evaporation.

How Much Water Loss Is Normal?

Before assuming you have a leak, it’s important to understand that some water loss is expected.

Most pools lose approximately:

• 1/8″ to 1/4″ of water per day

• Approximately 1-2 inches per week under normal conditions

Factors that increase evaporation include:

• High temperatures
• Direct sunlight
• Wind
• Low humidity
• Heated pool water

When water loss consistently exceeds normal evaporation rates, further investigation is usually warranted.

1. Underground Plumbing Leaks

One of the most common causes of swimming pool leaks is underground plumbing failure.

Pool plumbing lines are buried beneath decks, patios, and landscaping, making them impossible to inspect visually.

Common causes include:

• Ground movement
• Freeze-thaw cycles
• Pipe separation
• Cracked fittings
• Aging plumbing components

Because these leaks occur underground, homeowners often have no visible indication of the problem until significant water loss occurs. Underground plumbing failures are among the most frequently misdiagnosed pool leaks because the source cannot be seen directly.

Common Signs

• Wet or soggy areas around the pool
• Air bubbles from return jets
• Difficulty maintaining pump prime
• Water loss that changes when the pump is running

If you suspect a plumbing issue, learn more about underground pool plumbing leaks.

2. Pool Light Leaks

Pool lights are one of the most common structural leak locations we encounter.

Many homeowners assume the light fixture itself is leaking, but in many cases the problem is actually occurring behind the light niche.

Water can escape through:

• Light conduits
• Failed sealants
• Cracks around the niche
• Aging materials

Because these leaks occur below the waterline, they’re often difficult to identify without specialized leak detection equipment. Pool light conduit leaks are widely recognized as a common source of hidden water loss.

Common Signs

• Water loss that remains consistent regardless of pump operation
• Pool water stopping near the light level
• No visible plumbing issues

Almost all pool light leaks can be repaired underwater without draining the pool.

3. Skimmer Leaks

Skimmers are another extremely common leak source.

The skimmer sits at the waterline and is exposed to constant expansion, contraction, and movement over time.

As pools age, cracks can develop where the skimmer body meets the surrounding pool structure.

Common Signs

• Water level drops to the bottom of the skimmer opening
• Visible cracks around the skimmer
• Water loss near the tile line

Skimmer leaks are particularly common in concrete and gunite pools.

4. Return Fitting Leaks

Return fittings are the openings where filtered water returns to the pool.

Although relatively small, these fittings are common leak locations because they penetrate the pool wall and rely on seals and fittings that can deteriorate over time.

Common Signs

• Water loss near return levels
• Leaks detected around wall penetrations
• Aging or damaged fittings

These leaks are often repairable without major construction when identified early.

5. Vinyl Liner Leaks

Vinyl liner pools can develop leaks from:

• Punctures
• Tears
• Seam separations
• Aging liner material
• Damage from pool cleaners or toys

Even a small hole can lead to significant water loss over time.

Vinyl liner pools have more potential leak points than many homeowners realize because openings are cut into the liner for:

• Lights
• Skimmers
• Returns
• Main drains
• Steps

Each of these penetrations can become a potential leak source.

Common Signs

• Constant water loss
• Water loss unaffected by pump operation
• Visible liner damage
• Water stopping at a consistent level

6. Main Drain Leaks

Main drain leaks are less common than some other leak sources, but they can occur.

Potential causes include:

• Broken drain lines
• Cracked drain pots
• Structural failures near the drain

Because the main drain sits at the deepest point of the pool, leaks in this area often require specialized testing methods to confirm.

Common Signs

• Water loss continues until reaching the drain level
• Water loss remains consistent
• Other leak sources have been ruled out

7. Pool Equipment Leaks

Sometimes the leak isn’t in the pool at all.

Equipment pad leaks can develop around:

• Pumps
• Filters
• Heaters
• Valves
• Plumbing connections

These leaks are often easier to identify because they’re visible above ground.

Common Signs

• Wet equipment pads
• Water around pumps or filters
• Visible dripping
• Water loss occurring only when the system is running

Equipment leaks are frequently overlooked because homeowners focus exclusively on the pool itself.

8. Cracks in Concrete or Gunite Pools

Concrete and gunite pools can develop structural cracks over time.

Common causes include:

• Ground movement
• Settlement
• Freeze-thaw cycles
• Age
• Construction defects

Not all cracks leak, but some can allow significant amounts of water to escape.

Common Signs

• Visible cracking
• Water loss that doesn’t change with pump operation
• Water loss that stops at a specific level

Structural leaks often require professional evaluation to determine whether the crack is cosmetic or actively leaking.

Why Proper Pool Leak Detection Matters

One of the biggest mistakes homeowners make is assuming they already know where the leak is located.

The reality is that symptoms can be misleading.

For example:

• Air bubbles may suggest plumbing problems but originate elsewhere.
• Water stopping at a certain level may indicate several possible leak sources.
• Wet areas in the yard don’t always pinpoint the actual leak location.

We routinely encounter situations where homeowners have already spent money on repairs that didn’t solve the problem because the original diagnosis was incorrect.

Accurate leak detection is often more important than the repair itself.

When to Call a Professional

Professional leak detection should be considered when:

• Water loss exceeds normal evaporation
• The source of the leak is unclear
• You’ve already attempted repairs
• Water loss continues despite previous work
• Multiple leak sources may exist

Our Pool Pressure Testing Guide explains how pressure testing is used to confirm plumbing leaks and eliminate guesswork.

Need Professional Pool Leak Detection?

If your pool is losing water and you’re not sure why, Atlantic Pool Leak Detection can help.

We specialize in finding and diagnosing swimming pool leaks in vinyl liner, fiberglass, and gunite pools throughout New Jersey and Staten Island.

Before spending money on repairs, get an accurate diagnosis first.

Call 732-333-3304 or contact Atlantic Pool Leak Detection to schedule professional leak detection services.

Frequently Asked Questions

Categorised in: FAQ Blog, Pool Leak Inspection