Should you drain an above ground pool for winter?

No. Never drain an above-ground pool completely for winter. The water is what holds the wall round and braced against frozen ground and wind load, and an empty vinyl liner shrinks and hardens in the cold so it will not stretch back over the wall in spring. Lower the level only 4 to 6 inches below the skimmer with a solid cover, or 1 to 3 inches below the return with a mesh cover that lets rain and snowmelt through. In a mild climate with no freeze risk, you can leave the water at its normal level and simply plug the skimmer.

What temperature should you close a pool at?

Close once the water holds consistently below 60°F, not by a date on the calendar. Below 60°F algae growth effectively stops and chlorine demand falls to almost nothing, so winterizing chemicals last through the season. Close while the water is still 75°F and warm autumn weather returns, and you can open in spring to a green pool despite having done everything else correctly. In the northern half of the country that usually means late September to mid October; in the Southeast, November.

Do you need an air pillow in an above ground pool?

In any climate that freezes, yes. The pillow sits under the cover in the middle of the pool and compresses as ice forms, absorbing the expansion that would otherwise push outward against the pool wall. It also keeps the cover crowned so rain and snowmelt run to the edges instead of pooling in the center. Inflate it to about 60 to 80 percent, not fully, because a taut pillow bursts on the first hard freeze. Tie it to opposing sides so it cannot drift.

Can you leave the pump running all winter instead?

Only in mild climates where a hard freeze is genuinely unlikely, and even then it is a gamble. Running the pump prevents freezing while power holds, but a single overnight outage during a cold snap will freeze and split the pump housing, the filter tank and the plumbing. Above-ground equipment sits fully exposed with no insulation from the ground, so it freezes faster than in-ground plumbing. In any climate with real winter, disconnect and drain everything and store the pump indoors.

How much water should be on top of a winter cover?

As little as possible. A few inches of rainwater is normal and helps hold the cover down, but standing water beyond that stretches the cover, drags it into the pool and becomes a drowning hazard as well as a mosquito breeding site. Use a cover pump to keep it to two inches or less, and check after every heavy rain and every thaw. Cover-pump failure and the resulting collapse is the most common winter loss owners report.

How Do You Winterize an Above Ground Pool? Step-by-Step

Written & researched by Derek Holt Home & Appliances Editor

Updated October 2026

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Winterize an above ground pool once water temperature holds below 60°F. The sequence is: deep clean, balance the chemistry to pH 7.2 to 7.6 and alkalinity 80 to 120 ppm, add winterizing shock and algaecide, remove ladders and returns, lower the water 4 to 6 inches below the skimmer for a solid cover, disconnect and fully drain the pump, filter and hoses, plug the skimmer and return, float an air pillow, and fit and secure the cover. Never drain the pool completely. The water is what holds the wall round through the winter.

When should I close the pool?

Water temperature decides, not the calendar. At 60°F and below, algae growth effectively stops and chlorine demand drops to near zero, so the winterizing chemicals you add will still be doing their job in April. Close a pool at 75°F and those chemicals are consumed within weeks, which is the single most common reason people open a green pool in spring after doing everything else right. Buy a $10 floating thermometer and wait for three consecutive days under 60°F. In the Upper Midwest and Northeast that is typically late September to mid October, in the mid-Atlantic mid to late October, and in the Southeast often November.

Overhead view of a person skimming leaves from the surface of a backyard pool, in bright midday sun

What chemistry do I need before closing?

Balance the water 24 to 48 hours before you cover it, with the pump running so everything mixes. Balanced water protects the liner through five months of no circulation; unbalanced water etches, stains or wrinkles it. Test and correct in this order, because each reading affects the next.

Reading	Closing target	Why it matters over winter
Total alkalinity	80 - 120 ppm	Buffers pH so it does not drift acidic and etch the liner
pH	7.2 - 7.6	Low pH attacks vinyl and metal; high pH scales
Calcium hardness	175 - 275 ppm (vinyl)	Low calcium makes water aggressive to metal parts
Free chlorine	Shock to 10 - 12 ppm, let fall to 3 - 5	Kills what is in the water before it goes dormant
Cyanuric acid	30 - 50 ppm	Protects the residual on sunny winter days
Algaecide	Polyquat 60, per label	Copper-free, will not stain a vinyl liner

Use a polyquaternary algaecide rather than a copper-based one. Copper algaecides sitting in still water for months are a common cause of the blue-green liner staining owners discover at opening. Add shock first and algaecide 24 hours later, since high chlorine destroys algaecide on contact.

Over-the-shoulder view of a person skimming leaves from the surface of a backyard pool, in warm late-afternoon light

What is the full closing sequence?

Clean thoroughly. Brush walls and floor, vacuum to waste, net everything out. Organic debris left on the floor consumes chlorine all winter and stains vinyl.
Balance and shock per the table above, running the pump 24 hours to circulate.
Clean the filter. Backwash a sand filter, or hose and soak a cartridge — see how often to clean a pool filter cartridge. Store cartridges dry indoors.
Remove everything removable. Ladder, steps, solar cover, skimmer basket, return eyeball fittings, floats, thermometer. Store dry and out of the sun.
Lower the water. 4 to 6 inches below the skimmer opening for a solid cover, 1 to 3 inches below the return for a mesh cover, which admits precipitation and will refill through the winter.
Disconnect and drain the equipment. Pull every drain plug on the pump and filter, tip both to empty, disconnect the hoses and drain them, and store the pump indoors. Water left in a pump volute cracks the housing at the first hard freeze.
Plug the openings. A winter skimmer plug or an expansion plug in the return, plus a skimmer gizmo if your skimmer will still hold water. The gizmo compresses instead of the skimmer wall.
Float the air pillow. Inflate to 60 to 80 percent, center it, and tie it to opposite sides so it cannot drift to the edge.
Fit and secure the cover. Cable and winch through the grommets, then wall clips or cover seal to stop wind lifting it. A cover that gets under the wind is a cover that ends up in the pool.
Check monthly. Pump standing water off the cover, clear heavy snow at the edges, and confirm the cover is still sealed.

Golden-hour view of a person skimming leaves from the surface of a backyard pool

What goes wrong most often?

Four failures account for most winter damage. Draining the pool completely, which lets the wall lose its bracing and the liner shrink beyond recovery. Leaving water in the pump or filter, which splits the housing and turns a $0 job into a $300 replacement. Closing too warm, which spends the winterizing chemicals early and delivers a green pool at opening. And letting water accumulate on the cover, which drags the cover in, contaminates the water and can collapse a wall section under the weight. A cover holding four inches of water over an 18-foot round pool is carrying more than 5,000 pounds.

Cold water is also hard on liners. Freeze-thaw cycling and UV are the two things that age vinyl fastest, which is why closing properly extends liner life materially — see how long an above ground pool liner lasts.

Does this change by climate?

Yes. In the Sun Belt where the water never approaches freezing, many owners do not close at all. They keep the cover on, run the pump a few hours a day, and maintain a low chlorine residual through the winter — which is often less work than a full close and open. In the freeze belt the full sequence above is not optional. In transitional zones such as the Carolinas, north Texas and the Pacific Northwest, the practical approach is to close the plumbing and equipment as if it will freeze, because it occasionally does, while treating the water as a mild-climate pool.

Local ordinances on pool barriers, fencing and covers still apply through the off-season, and several states require a compliant barrier year round regardless of whether the pool is in use. Check your municipal code.

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How Do You Winterize an Above Ground Pool?