Last updated: July 2026
Winterize your above ground pool when nighttime temperatures consistently drop below 50°F (10°C). The process takes 2–3 hours and involves balancing the water chemistry, lowering the water level, removing and storing the pump and accessories, and covering the pool. Skipping any step — especially pump removal and chemical balancing — typically results in green water in spring and possible liner or equipment damage.
| When to winterize: the 50°F rule Start winterizing when nighttime temperatures consistently fall below 50°F (10°C). At 50°F and below, algae growth slows dramatically, which means your closing chemicals will remain effective through the winter without being consumed by biological activity. Closing too early (water still warm): closing chemicals burn off before spring. Closing too late (water already freezing): risk of freeze damage to pump, fittings, and liner. In most of the northern US: mid-September to mid-October is the typical closing window. In the southern US (mild winters): some pools can stay open year-round with reduced chemical dosing. |
What You’ll Need
| Item | Purpose | Where to Buy | Approx. Cost |
|---|---|---|---|
| Pool closing chemical kit | Algaecide + stain preventer + shock for winter | Doheny’s, In The Swim, Amazon | $20–45 |
| Pool shock (calcium hypochlorite) | Super-chlorinate before closing | Pool retailer, hardware store | $15–25 |
| pH Down (sodium bisulphate) | Adjust pH to 7.2–7.4 before closing | Pool retailer | $8–15 |
| Winter above ground pool cover | Protect pool from debris, snow, UV over winter | Amazon, pool retailer | $30–80 |
| Winter cover cable + winch | Secure cover against wind | Amazon, pool retailer | $15–25 |
| Air pillow (optional but recommended) | Support cover under snow weight, prevent ice expansion damage | Amazon, pool retailer | $10–25 |
| Garden hose | Lower water level to correct depth | Hardware store | — (you likely have one) |
| Submersible pump (optional) | Faster water level lowering than gravity drain | Hardware store, rent | $40–80 or rent |
| Storage bags / boxes | Protect pump, filter, ladder, and accessories during storage | — | — |
Step-by-Step Winterizing Process
Step 1: Test and Balance Water Chemistry (1–2 days before closing)
Balanced water at closing protects the liner and equipment from corrosion and staining over winter. Test and adjust to these targets before adding any closing chemicals:
- pH: 7.2–7.4 (slightly lower than normal operating range, as pH drifts up over winter)
- Total Alkalinity: 80–120 ppm
- Calcium Hardness: 175–225 ppm
- Free Chlorine: 1–3 ppm (you’ll super-chlorinate in a later step)
Correct any out-of-range readings 24–48 hours before closing. Don’t try to adjust and close on the same day — the chemicals need time to circulate and take effect.
Step 2: Super-Chlorinate (Shock) the Pool
- Add pool shock at 2x the normal dosage for your pool volume. This kills any remaining algae and bacteria before closing.
- Run the pump for at least 8 hours after adding shock to circulate it fully.
- Wait until the free chlorine level drops back below 5 ppm before adding algaecide in the next step. High chlorine degrades algaecide on contact.
Step 3: Add Winter Closing Chemicals
- Add a winter algaecide (60% or higher concentration recommended for season-long effectiveness). Follow dosage on the product label for your pool volume.
- Add a metal stain preventer/sequestrant if your water has high iron or copper content. This prevents metal staining on the liner over winter.
- Add a pool closing floater or slow-dissolve closing chemical kit if using one. These release algaecide and clarifier gradually over the winter months.
- Run the pump for 4–6 hours to distribute closing chemicals evenly.
Step 4: Lower the Water Level
The target water level for winter storage depends on your climate and cover type:
- Standard winter cover (no ice expected): lower water to 4–6 inches below the skimmer/return jet openings. This prevents water from entering the skimmer and freezing.
- Harsh winter climate (significant ice expected): lower water to 6–12 inches below the return jet. Expanding ice needs space.
- Mild climate (no hard freeze expected): water level can stay at 4–6 inches below returns, or some owners keep it at near-normal level with just a cover.
Use the pool’s drain adapter with a garden hose to lower the level. A submersible pump speeds this up significantly for large pools.
| ⚠️ Do NOT fully drain an above ground pool for winter A fully drained above ground pool liner will collapse inward under wind pressure and the weight of any snow on the cover. A collapsed liner almost always requires replacement — the creases and stress points from collapse crack the vinyl. Always leave water in the pool over winter. The water weight keeps the liner in position. The only exception: inflatable pools should be fully deflated, drained, and stored indoors in cold climates. |
Step 5: Remove, Clean, and Store the Pump and Filter
- Turn off and unplug the pump.
- Disconnect all hoses from the pump and filter. Drain all water from the pump, filter housing, and hoses completely.
- Remove the filter cartridge. Rinse it clean with a garden hose and allow to dry completely before storage.
- Store the pump, filter, and cartridge indoors — garage, shed, or basement. Temperatures below freezing will crack pump housings and damage impellers.
- Cap the pool’s inlet and outlet ports with the included plugs to prevent debris entry over winter.
| Why pump storage matters: freeze damage is irreversible A pump left outside through freezing temperatures will crack at the impeller housing or volute where water is trapped. Replacement pumps cost $60–200. A 10-minute indoor storage step prevents this cost every winter. The filter cartridge left outside over winter develops mildew and the pleated material becomes brittle. Store it dry, indoors. |
Step 6: Remove Pool Accessories
- Remove and store the pool ladder. Leaving the ladder up over winter is both a safety concern (unsupervised pool access) and unnecessary wear on the ladder hardware.
- Remove any pool lights, thermometers, floaters, and skimmer baskets.
- Remove the solar cover if you use one. Fold it dry and store indoors — solar covers left on over winter under snow and ice get damaged.
Step 7: Install the Air Pillow (Recommended)
An air pillow is an inflatable cushion placed at the centre of the pool under the winter cover. It’s not strictly required but is highly recommended in climates with heavy snow or ice:
- It prevents ice from forming as a solid sheet across the entire pool surface. Ice that forms in one connected sheet can expand with nowhere to go except outward, putting pressure on the pool walls and liner.
- With an air pillow, ice forms around the edges only, with the pillow occupying the centre. The ice can move toward the centre (compressing the pillow) rather than pushing outward against the walls.
- Inflate the pillow to about 60–70% capacity — not fully inflated. A fully inflated pillow is more likely to puncture under snow weight. Tie it to the pool drain or a stake in the centre of the pool.
Step 8: Install the Winter Cover
- Centre the winter cover over the pool. A winter pool cover should overlap the pool edge by at least 12–18 inches all around.
- Thread the cover cable through the grommets around the cover’s edge and tighten the winch or ratchet to pull the cover taut and secure it against wind.
- For extra security in windy locations: place water bags (or bags of sand) around the cover edge on the outside of the pool wall to prevent wind from lifting the cover.
- Check that no standing water has pooled on top of the cover after installation. Pooled water adds significant weight and strains the cover and cable system. Use a cover pump (electric or manual) to remove standing water as needed through the winter.
Climate-Specific Notes
| Climate Type | Key Differences | Additional Steps |
|---|---|---|
| Northern US / Canada (hard freeze, heavy snow) | Full protocol above is essential. Snow load on cover is significant. | Use heavy-duty winter cover rated for local snow load. Air pillow is critical. Check cover periodically through winter for ice/water accumulation. |
| Mid-Atlantic / Midwest (moderate freeze) | Standard protocol applies. Some winters mild, some harsh. | Air pillow recommended. Standard winter cover adequate. Check cover after major snow events. |
| Southern US (mild winter, light or no freeze) | Water level drop less critical. Pump may stay in mild-climate winters. | Lighter winter cover or solar cover may be sufficient. Continue monitoring chemistry monthly even in mild winters — algae grows slowly but doesn’t stop entirely above 50°F. |
| Pacific Northwest / coastal mild climates | Rain is the primary concern — cover water accumulation. | Focus on cover integrity and drainage. Air pillow less critical. Check cover weekly for pooling water from rain. |
Opening the Pool in Spring
Proper winterization makes spring opening significantly faster and cheaper. A correctly closed pool should re-open with water that’s still relatively clear and chemically balanced rather than the green, algae-filled water that results from skipped closing steps.
- Remove the cover: drain any standing water from the top first, then remove and dry the cover before storing.
- Reconnect the pump and filter. Prime the pump before running — a dry-running pump damages impellers.
- Raise the water level to operating level.
- Test and balance water chemistry before swimming. pH, alkalinity, and chlorine will all need adjustment after winter.
- Run the pump for 24–48 hours continuously before the first swim to fully circulate and filter the winter-stored water.
Frequently Asked Questions
When should I close my above ground pool for winter?
When nighttime temperatures consistently drop below 50°F (10°C). This is typically mid-September to mid-October in the northern US and Canada, and later (or not at all) in southern states. Closing when the water is still warm (above 65°F) wastes closing chemicals, as they burn off faster in warmer water.
Can I leave my above ground pool up all winter?
Yes — above ground pools can be left assembled over winter with proper winterization. The frame stays up, the liner stays in (with lowered water level), and the cover keeps debris out. What you must remove is the pump, filter, and all accessories — these will be damaged by freezing if left outside. Do not fully drain the pool; the water weight keeps the liner properly positioned.
Do I need to drain my above ground pool for winter?
No — and you shouldn’t fully drain it. A drained above ground pool liner will collapse under wind pressure and snow weight, almost always requiring full liner replacement. Lower the water level to 4–12 inches below the return jets (depending on climate severity) but always leave water in the pool.
What happens if I don’t winterize my above ground pool?
In a cold climate: water freezing inside the pump, filter, and hoses will crack these components. The pump will need replacement in spring ($60–200). If ice forms as a solid sheet across the full pool surface, it can expand and push against the pool walls, causing liner tears and potentially frame damage. In spring, the water will likely be green with algae, requiring $30–60 in shock treatment and significant filtration time to clear.
Can I use a regular tarp instead of a winter pool cover?
A heavy-duty blue tarp can work for mild climates, but it’s not ideal. Winter pool covers have grommets for the cable system that secures them against wind — a tarp without grommets will blow off in any significant wind. For climates with snow, a proper winter pool cover rated for local snow load is worth the $30–80 investment to avoid the tarp blowing off mid-winter.
How do I keep my pool water from turning green over winter?
Follow steps 2 and 3 above: super-chlorinate before closing, then add a winter algaecide and closing chemical kit. The combination of high initial chlorine level and slow-release algaecide keeps algae suppressed through most winters. In mild climates where the water stays above 50°F year-round, check the water monthly and add algaecide as needed — algae grows slowly but continuously at temperatures above 50°F.