Is Your Closed Pool Losing Water This Winter? How to Tell a Leak From Normal Loss

Published November 6, 2026 · A Clear Alternative Water, Pennsauken NJ, since 1991

A closed pool should hold its water level through a South Jersey winter, apart from small changes from rain, snowmelt and cover pumping. Evaporation is very low in cold weather, especially under a cover, so a level that keeps dropping week after week usually points to a leak. Check the level every few weeks against where you left it at closing. If it falls with no storm or cover pumping to explain it, stop adding water, note where the level settles, and plan a leak check before spring. A Clear Alternative delivers pool water across eight South Jersey counties for spring refills; call 856-856-5210 any time.

How Much Water Loss Is Normal

In summer, an open pool can lose one to two inches a week to evaporation, more in hot, dry, windy weather. The EPA's WaterSense guide to pool water efficiency suggests checking for a leak when a pool loses more than about two inches a week. In winter the numbers are much smaller. Cold water and cold air evaporate slowly, and a cover blocks most of what is left. A covered pool in a New Jersey winter should lose very little to evaporation.

Winter has its own ways of changing the level, though:

• Rain and snowmelt pass through a mesh safety cover and raise the level.
• Cover pumping on a solid cover can pull pool water out if the cover has a tear or the pump sits in a low spot touching pool water.
• Ice can make the level hard to read and hold water above the true line.

Signs Your Closed Pool Has a Leak

• The water level is well below where you left it at closing, with no cover pumping or big storm to explain it.
• A solid cover pulls tight, slides toward the water, or tears at the grommets and seams. In The Swim lists this as a common sign of a winter leak.
• Soft, soggy or unusually green ground near the pool, the skimmer, or the equipment pad.
• Cracked or shifted tile, coping or decking.
• On a vinyl pool, wrinkles or a liner pulling away from the wall or out of its track.
• On an above-ground pool, a wall that bulges, leans or changes shape.

How to Check the Level Without Opening the Pool

1. Use your closing mark. If you marked the water line on the skimmer or tile at closing, compare to that. If not, measure down from the coping or top rail now, and write it down with the date.
2. Check after a quiet stretch. Pick a week with no heavy rain, snowmelt or cover pumping.
3. Look at the same spot each time. On a safety cover, you can often see the water through the mesh near the skimmer. On a solid cover, check at a corner where you can lift the edge safely.
4. Keep a simple log. Date, measurement and weather. A steady drop is the pattern to watch for.

Never walk on a pool cover or lean over icy coping to take a reading. If you cannot measure safely, wait for a mild day.

The Bucket Test

The bucket test is the standard way to tell evaporation from a leak, and it works best in spring or fall when the water is uncovered and not frozen. The EPA WaterSense steps are simple:

1. Pick a day without rain or heavy wind and turn off any automatic fill.
2. Fill a bucket with pool water to about an inch from the top and set it on a step, so it sits partly submerged.
3. Mark the water level inside the bucket and the pool level on the outside of the bucket.
4. Wait 24 hours and compare.

If the pool dropped more than the bucket, water is leaving some way other than evaporation. Many pool pros run the test twice, once with the pump on and once with it off. A bigger loss with the pump running points to the plumbing; a loss either way points to the shell or liner. In winter, with the cover on, a bucket test is hard to do well, which is why tracking the level over several weeks is more useful.

What to Do If the Level Keeps Dropping

Stop Topping It Off

Adding water hides the problem and can wash out soil around a leaking pipe or behind a liner. Let the level drop and see where it stops.

Watch Where It Stops

A leak usually stops once the water falls below it. If the level settles just under the skimmer, the skimmer or its seal is a likely suspect. If it settles at the light or a return, look there. In The Swim notes that a stain line or debris stuck to the wall at the new level can also help locate it.

Protect the Cover and Liner

If the water gets too low under a solid cover, the cover loses its support and can sag or tear under snow. On a vinyl pool, a liner left above the water can dry out and shrink. If the drop is large, call a pool service or leak detection company about whether to add water to a safe level for the rest of winter.

Plan the Repair for Spring

Most leak repairs, especially underground plumbing or liner work, wait until the pool is opened. Book a leak detection visit early so the repair can be finished before the pool is refilled for the season.

Above-Ground Pools

Above-ground pools are especially sensitive to winter water loss, because the water helps hold the walls and liner in shape. Check the level more often, look for wet ground under the wall, and inspect the skimmer and return fittings, which are common leak points. Never let an above-ground pool drain completely.

Common Winter Leak Spots

• Skimmer: the seal between the skimmer and the pool wall, or a crack in the skimmer body from freezing.
• Return fittings and lights: gaskets and the conduit around a pool light.
• Underground plumbing: a line that was not fully blown out and plugged can freeze and crack.
• Liner tears: branches, ice or animals can puncture a vinyl liner under the cover.

Planning Your Spring Refill

A pool that leaked over winter usually needs more water at opening than a normal top-off. After the leak is fixed, you may need to bring it back up several inches or a few feet, or refill completely after a liner replacement. Our guide to how many gallons your pool holds helps you estimate how much, and our guide on refilling after a liner replacement covers that case. If you have not closed yet, our pool closing guide explains the right winter water level. Our pool fill page explains how a delivery works.

Serving Eight South Jersey Counties

We deliver pool water in Burlington, Camden, Gloucester, Atlantic, Salem, Cape May, Mercer and Monmouth counties. See our service areas for the towns we cover.

When to Call A Clear Alternative

Call us once a leak is repaired and the pool is ready to refill, when you open a pool that lost a lot of water over winter, or when a new liner needs a fast fill. Our tankers carry 6,200 gallons, so most refills take a few loads, not days of running a hose. A Clear Alternative is a family-run company that has served South Jersey since 1991 from 9230 Collins Ave in Pennsauken. Call 856-856-5210 any time, reach our office at 856-663-8088, or request a quote online.

Frequently Asked Questions

Is it normal for a closed pool to lose water in winter?

Only a little. Evaporation is very low in cold weather, especially under a cover. A level that keeps dropping with no rain, snowmelt or cover pumping to explain it usually means a leak.

How much water loss means a pool has a leak?

The EPA's WaterSense guidance suggests checking for a leak when a pool loses more than about two inches a week. In winter, with a cover on, even less loss is a warning sign.

How do I do a pool bucket test?

Fill a bucket with pool water, set it on a step, and mark the water inside the bucket and the pool level outside it. After 24 hours, if the pool dropped more than the bucket, water is leaving some way other than evaporation.

Should I keep adding water to a leaking closed pool?

Generally no. Topping off hides the problem. Let the level drop to see where it stops, which helps locate the leak, and ask a pool professional if the level gets low enough to risk the cover or liner.

Can a pool leak be fixed in winter?

Most leak repairs wait until the pool is opened in spring. Book leak detection early so the repair is done before the seasonal refill.

Can you refill my pool after a leak repair?

Yes. We deliver pool water in Burlington, Camden, Gloucester, Atlantic, Salem, Cape May, Mercer and Monmouth counties. Call 856-856-5210 to schedule.