Why a Pool Leak Should Be Detected Before Closing for Winter

Written by Randy Racioppi, founder of Atlantic Pool Leak Detection, with more than 15 years of experience locating pool leaks throughout New Jersey and Staten Island.

A swimming pool should never be closed for the winter knowing that it is leaking. Once the pool is winterized and covered, the leak may not stop, and the pool may continue losing water for weeks or even months.

By spring, the pool could be nearly or completely empty. That can cause damage to the safety cover, vinyl liner, pool walls, plaster finish, or the pool structure itself.

If the leak has not been located and resolved by your scheduled closing date, postpone the closing and address the leak first. Rescheduling may be inconvenient, but repairing damage caused by a pool that loses too much water over the winter can be far more expensive and difficult to deal with.

Winterizing Does Not Automatically Stop a Pool Leak

During winterization, plumbing lines are normally blown out and plugged. This may isolate a leak within a properly winterized plumbing line, but it will not stop leaks in components that remain underwater.

Water can continue leaking through a vinyl liner, pool shell, skimmer, light niche, return fitting, main drain, around steps, or other areas below the waterline. A pool can also have more than one leak.

This is why the leak must be detected before the pool is closed. Do not assume winterization will stop water loss when the leak’s location is unknown.

Low Water Can Damage a Winter Safety Cover

The water inside the pool helps support a safety cover when snow and ice accumulate on top of it. If a leak causes the water level to drop, the cover may be forced to carry more weight than normal because it no longer has adequate support underneath.

New Jersey and Staten Island can experience major winter storms that leave large amounts of snow and ice on pool safety covers. When that snow freezes, partially melts, refreezes, and remains for weeks or even months, the resulting weight can be substantial.

If a pool is closed with a known leak and the water level falls too low, the cover is left with less support precisely when it may be carrying its greatest load. The cover may stretch, tear, or pull excessively against its straps, springs, and anchors. This can result in the safety cover needing to be repaired or replaced, potentially costing thousands of dollars.

An Empty Vinyl Liner Pool Can Suffer Major Damage

In a vinyl liner pool, the water holds the liner in place while providing support for the pool walls.

As the water level falls, the liner can move, stretch, contract, pull out of its track, or develop wrinkles. Wrinkling is especially common after a vinyl liner pool loses too much water. Groundwater can also collect behind the liner, causing it to float or shift.

If the pool leaks to the point of being empty, the walls can bend, bow inward, or potentially collapse without the outward pressure provided by the pool being full of water. A repairable leak can turn into a liner replacement, wall repair, or even major reconstruction.

Gunite and Fiberglass Pools Can Lift Out of the Ground

The water inside a gunite (concrete) or fiberglass pool provides weight that helps counteract hydrostatic pressure from groundwater beneath and around the pool. This is especially important in areas with a high-water table or known groundwater issues.

If the water level inside the pool drops significantly while groundwater remains high outside it, the resulting hydrostatic pressure can cause the pool shell to shift, crack, or lift out of the ground. This is commonly referred to as the pool “popping.”

A pool does not have to be intentionally drained for this danger to exist. If a leak causes the water level to drop far enough, it can create the same imbalance between the weight inside the pool and the hydrostatic pressure surrounding it.

A Real Example From Manalapan, New Jersey

In one incident in Manalapan, a cover pump accidentally fell into an inground pool and pumped out the pool water. A leak did not cause the water loss, but once the pool became empty, hydrostatic pressure lifted it approximately two feet out of the ground.

The cause was different, but the example demonstrates the danger created by an empty pool. A known leak that continues throughout the winter can eventually create the same imbalance between the empty pool and the groundwater surrounding it.

An Empty Concrete Pool Can Damage the Plaster

The plaster finish inside a gunite or concrete pool is intended to be wet. If a leak leaves the plaster dry for an extended period, it may deteriorate, shrink, crack, develop hollow areas, or delaminate from the pool shell. Freezing temperatures can create additional stress. Even if the shell does not move, the interior finish may require significant repair or resurfacing, which can be very expensive.

Delay the Closing Until the Leak Is Resolved

Many homeowners schedule their pool closing weeks or months in advance. That appointment should not become the reason for closing a pool with a known leak.

Closing the pool and “dealing with it next spring” is not a good solution. The closing can be rescheduled. Damage to the liner, pool walls, plaster, safety cover, or pool structure could be far more problematic and expensive to resolve if the pool continues leaking over the winter.

Postpone the closing, complete the leak detection, and resolve the problem before the pool is winterized.

Find the Leak Before You Cover the Pool

A winter safety cover can hide a pool from view, but it cannot protect the pool from an active leak underneath it.

Atlantic Pool Leak Detection provides professional pool leak detection throughout New Jersey and Staten Island. Depending on the pool and reported symptoms, testing may include an underwater inspection, dye testing, individual plumbing-line pressure testing, and electronic listening to pinpoint an underground plumbing leak.

If your pool is losing water, contact Atlantic Pool Leak Detection before closing it. Tell us how much water the pool is losing, whether the loss changes with the equipment running, the type of pool, and the scheduled closing date.

If the pool has already been winterized and you discover that the water level is dropping, read our separate guide, Pool Leaking in Winter? What Homeowners Need to Know, for the steps to take after closing.

Frequently Asked Questions