Above Ground Pool Water Level in Winter: Why Draining Too Much Collapses the Walls

Why the Water Level You Leave Behind Matters

An above ground pool wall is not really holding itself up. Water pressure pushing outward against the liner and the wall is what keeps that wall standing upright and rigid, and the frame around it is mostly there to keep the shape, not to bear a serious structural load on its own. Drain the pool down for winter and you take away the one thing doing most of the work.

I have walked into more than one backyard in April to find a wall buckled inward or a whole section leaning, and in almost every case the owner had drained the pool close to empty in the fall because it seemed like the responsible thing to do before winter. It is the opposite of responsible. The correct move is leaving enough water in the pool that the wall keeps its support, while still protecting the plumbing from freeze damage.

What Actually Happens When a Pool Is Drained Too Low

Home improvement guidance on this is direct about the mechanism: Family Handyman explains that water in the pool is what helps keep the walls upright, and the less water sitting in there, the more likely snow load and ice end up pulling the wall down instead. What is left facing a whole winter is a thin metal or resin wall carrying snow weight, ice, and wind pressure with nothing behind it pushing back. A pool drained down to only a few inches behaves more like an unsupported shell than a supported pool wall.

Frost heave adds another layer to the problem. Ground around and under the pool can shift slightly as it freezes and thaws through the winter, and a wall with no water pressure behind it has far less resistance to that movement. Wind pressure on an empty wall behaves differently too, since there is nothing on the inside pushing back against a gust hitting the outside. None of these forces are dramatic on their own, but stacked together over a whole winter, they are exactly what turns a fine fall closing into a spring collapse.

Field Note: The worst case I have seen was a steel frame 18-foot pool drained almost completely by an owner trying to save on a winter cover. By March, one full wall section had folded inward under a heavy snow load, and the liner tore in the process. Even replacing the liner alone can be expensive, before you account for a bent wall panel.

The Two Water Level Options for Closing

There are two accepted approaches for handling water level at closing, and both are built around the same goal: keep enough water in the pool to support the wall while keeping water out of places where it can freeze and crack something.

The first option is lowering the water four to six inches below the skimmer opening, then plugging the return jet and skimmer inlet with rubber winterizing plugs so water cannot sit in either fitting and freeze. This is the approach most closing kits are built around, and it is well documented across pool retailer guidance as the standard method. The second option is leaving the water at its normal operating level, meaning wherever it sits during a normal summer with the pump running, and covering the skimmer opening with a skimmer guard or gizmo instead of draining at all. Some guidance treats this second approach as the safer choice in colder climates because it lets the owner keep the water at a normal level while still blocking the skimmer from freezing.

Key point: How to Choose the Safer Option for Your Situation. Choose lower-and-plug if your winters are mild to moderate and your closing kit already includes the right rubber plugs for your fittings. Choose normal level with a skimmer guard if you get heavy snow or repeated ice, want maximum wall support, and can confirm the guard actually seals your skimmer opening. If the water drops too low partway through winter from a slow leak or evaporation, check that the pool is still safe to approach and refill it back toward a supporting level before the next heavy snow or ice event, rather than waiting until spring.

Either option keeps the pool well ahead of a fully drained setup, and the real decision usually comes down to your climate and what your closing kit already includes.

Where the Partial Drain Approach Gets Risky

Some closing guides suggest draining down to below the return jets and stopping there, which is fine as a general rule in milder climates where snow load is light or infrequent. The problem shows up when that same 4 to 6 inch guideline gets stretched further than it should in a region that actually gets hit with heavy snow and repeated freeze-thaw cycles.

I have seen owners drain an extra foot or more past the recommended level because they were worried about ice expansion cracking the wall, which is a reasonable fear pointed at the wrong problem. Ice expansion is a plumbing issue, handled by plugging fittings and adding air pillows, not a reason to remove more water than necessary. Draining further than the 4-to-6-inch range in a heavy snow climate removes wall support at exactly the time of year that support matters most.

• Stick to the 4 to 6 inch guideline if you are lowering the water at all
• Do not drain further because you are worried about ice, that is a plumbing problem, not a water level problem
• In heavy snow regions, consider the normal-level skimmer guard approach instead of lowering at all
• Check the water level once or twice mid-winter if evaporation or a slow leak could be pulling it down further than intended

That last point catches people off guard. A pool closed correctly in October can still end up under-supported by February if nobody checks on it, especially with a slow leak nobody noticed during the summer.

What to Do About the Return Jet Fitting

The return jet fitting is a small detail that causes a disproportionate amount of spring frustration. If you leave the directional eyeball fitting in place over winter, any water trapped inside it can freeze and crack the fitting from the inside, and you will not know it happened until you turn the pump back on in spring and water starts spraying somewhere it should not.

Pull the eyeball fitting out and thread in a winterizing plug instead before you close for the season. It is a five-minute job while the pool is still at a workable water level, and it is a much smaller job than the alternative. A cracked return fitting is not expensive to replace on its own, typically five to fifteen dollars for the part, but replacing it means draining the pool back down below the jet line again to get access, which defeats the purpose of getting the water level right the first time.

Final Thoughts: Leave the Water Doing Its Job

The instinct to drain a pool for winter usually comes from good intentions, an owner trying to protect the equipment from freezing. The problem is that draining too far protects the plumbing while putting the wall itself at risk, and a collapsed wall is a far more expensive spring surprise than a cracked fitting. Pick either the lower-and-plug method or the normal-level skimmer guard method based on your climate, plug the return jet fitting properly, and check the water level again partway through winter if you can.

This decision is one piece of a larger seasonal above ground pool care routine. If you are working through the rest of the shutdown at the same time, the full above ground pool closing sequence covers where this water level step fits alongside chemical balancing and cover placement. For the bigger picture of keeping a pool in good shape from one season to the next, long-term above ground pool maintenance planning covers where winter water level fits alongside opening, closing, and the maintenance tasks in between. When spring comes around, the correct steps for opening in spring pick up right where this closing decision leaves off.

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