This is one of the most common questions we hear every fall, and also one of the most common mistakes homeowners make on their own. It comes up so often in our FAQs that it’s worth the full explanation here. Closing a pool doesn’t mean emptying it. Draining a pool completely before winter can actually cause more damage than leaving it alone entirely, sometimes worse than skipping the closing altogether. Here’s why the water needs to stay in your pool all winter, and what we do instead.
The Short Answer: No, and Here’s Why
You should never fully drain an inground pool for winter. The water in your pool isn’t just there for swimming, it’s doing structural work, counterbalancing pressure from the ground around and beneath the pool shell. Take that water away and you remove the one thing holding that pressure in check.
Why This Myth Sticks Around
It’s an easy assumption to make. Draining a pool at the end of the season feels a little like emptying a pool toy before putting it away for winter, and it lines up with how people handle other outdoor equipment that gets stored empty and dry. Pools don’t work that way. Unlike a garden hose or an above ground kiddie pool, an inground pool is built into the ground itself, and the water inside it is part of what keeps the structure in place, not just something to be poured out when the season ends. It’s a reasonable instinct that just doesn’t apply here, and it’s one of those assumptions that can cause real damage without anyone realizing why until spring.
What Actually Happens If You Drain It
An empty pool can develop cracks in the shell or shifting, bulging walls, and for vinyl liner pools, a liner that dries out, shrinks, and tears. Beyond the shell itself, tile lines can crack or pop off, and skimmer and light fixtures set into the walls can shift out of alignment when there’s nothing holding the surrounding structure steady. Repairs to fix any of this usually mean draining the pool anyway, on top of whatever damage prompted the situation in the first place, which is part of why prevention matters more here than with most home maintenance tasks. None of this is guaranteed the moment a pool is drained, but the risk builds the longer it sits empty, especially after heavy rain or in areas with a high water table, both common across Central Jersey.
Hydrostatic Pressure, Explained Simply
The ground around your pool holds groundwater, and that water pushes against your pool’s walls and floor from the outside. As AQUA Magazine’s coverage of pool construction failures explains, this hydrostatic pressure affects every inground pool, and the water inside your pool is what typically counteracts it. When the pool is full, the pressure pushing in and the weight pushing back stay in balance. Drain the pool, and only one side of that equation is left standing.
This isn’t just a concern for older pools or specific soil types either. Any inground pool sitting below the surrounding grade is affected, because groundwater collects in the space around the pool shell no matter what the pool itself is made of. Heavy fall rain, snowmelt, or a naturally high water table all raise that pressure. A pool that’s been drained can be pushed up out of the ground or have its walls bow inward within days under the wrong conditions, not months.
Concrete, Vinyl, and Fiberglass: Different Pool, Different Risk
How a drained pool responds depends partly on what it’s made of.
Concrete and Gunite Pools
Concrete and gunite pools are reinforced with steel and are generally more resistant to hydrostatic pressure than other pool types, but they’re far from immune. Once the counterbalancing weight of the water is gone, the surrounding pressure can still cause the pool to lift, shift, or crack, and repairing a cracked concrete shell is a much bigger job than avoiding the problem in the first place.
Vinyl Liner Pools
Vinyl liner pools face a different but equally serious risk. Without water behind it, a liner can dry out, shrink, and pull away from the walls, and it can happen faster than most people expect, sometimes within days depending on sun exposure and temperature. Once a liner has shrunk and wrinkled, it typically can’t just be stretched back into place.
Fiberglass Pools
Fiberglass pools carry their own version of this risk, and in some ways a more dramatic one. Because a fiberglass shell is lightweight compared to concrete, it’s actually more prone to floating or shifting out of the ground entirely when drained, especially if groundwater is high.
What We Actually Lower, and Why
Closing your pool does involve bringing the water level down, just not all the way. We lower it to just below the skimmer, low enough that water can’t get into the skimmer line or the pump and filter system when we blow those lines out, but nowhere close to empty. The rest of the pool stays full all winter, doing exactly the structural job it’s supposed to do.
What About Repairs That Require Draining?
There are situations where a pool genuinely needs to be partially or fully drained, a liner replacement, certain structural repairs, or specific equipment work. The difference is that this is done under controlled conditions, with a plan for how long the pool will be empty and what precautions are being taken in the meantime, not as a routine part of closing for the season. If a repair calls for draining, that’s a conversation to have with whoever is doing the work, not something to take on as a seasonal habit.
If Your Pool Has Already Been Drained
Sometimes a pool ends up empty for other reasons, a repair that required draining it, a liner replacement, or simply not knowing better before now. If that’s the situation you’re in, the priority is getting water back in as soon as possible, not waiting until your usual closing date. The risk isn’t measured in weeks so much as in weather. A dry stretch with low groundwater buys more time than a period of heavy rain or snowmelt, when the surrounding soil is saturated and pushing back harder. This is also why we don’t recommend leaving a pool empty over a weekend just to be safe while deciding on next steps. The safest move is almost always keeping water in the pool while you sort out whatever brought you to this point.
Protecting the Pool You Already Have
A proper Pool Closing Service visit protects two things at once: the equipment, by clearing water out of the lines and pump so nothing freezes and cracks, and the pool itself, by leaving enough water in place to keep it structurally sound until spring. It’s a small distinction on paper, water level down a few inches versus a pool sitting completely empty, but it’s the difference between a routine winter and a spring that starts with repairs instead of just reopening. It’s the same standard we hold every service under Pool Cleaning Service to, don’t fix one problem by creating another.
