The Definitive Guide To Closing Your Above Ground Swimming Pool For Winter

Successfully closing an above ground swimming pool requires a precise sequence of chemical balancing, mechanical drainage, and structural protection to prevent costly freeze-thaw damage. By maintaining a pH between 7.2 and 7.6, lowering water levels 6 inches below the skimmer, and utilizing an air pillow for ice expansion, you ensure the integrity of the vinyl liner and filtration system through the off-season.

Pre-Winterization Assessment and Equipment Inventory

Timing is the most critical factor in a successful pool closing. You should ideally begin the process once the ambient water temperature consistently drops below 65 degrees Fahrenheit (18 degrees Celsius). Closing the pool while the water is still warm encourages algae growth beneath the cover, leading to a "green opening" in the spring. Conversely, waiting too long risks the expansion of freezing water in the plumbing lines or the filter tank, which can cause catastrophic equipment failure.

Before beginning the physical labor, ensure you have the following specialized materials and tools on hand to avoid mid-process interruptions.

• Chemical Winterization Kit: Includes high-concentration algaecide (60% polyquat is preferred), non-chlorine oxidizing shock, and a metal sequestering agent to prevent staining.
• Water Testing Hardware: A high-quality DPD or digital test kit capable of measuring pH, Total Alkalinity, Calcium Hardness, and Cyanuric Acid.
• Expansion Protection: Heavy-duty air pillows (at least 4x4 or 4x5 feet) and Gizzmo-style skimmer compensators.
• Plumbing Plugs: Threaded or expansion rubber plugs for return jets.
• Winter Cover & Security: A solid or mesh winter cover with a high-tensile winch and cable system, plus optional wall clips or water bags for wind resistance.
• Mechanical Tools: A shop vacuum (for blowing out lines), a screwdriver set, and needle-nose pliers.
• Estimated Duration: 4 to 6 hours depending on pool size and debris levels.
• Budget Benchmark: $150–$400 for standard chemical kits and replacement covers.

Sequential Execution for Above Ground Pool Winterization

Step 1: Deep Cleaning and Debris Extraction

The presence of organic matter—leaves, insects, and silt—over the winter will consume your sanitizer and lower the pH, potentially etching the liner. Begin by vacuuming the pool floor thoroughly. If you have a sand filter, set the multiport valve to "Waste" to bypass the filter and remove heavy sediment directly. Scrub the walls with a nylon-bristled brush to loosen any bio-film or microscopic algae spores. Clear the skimmer and pump baskets of all debris.

Step 2: Chemical Balancing and LSI Management

Achieving a balanced Langelier Saturation Index (LSI) is vital because cold water is more corrosive than warm water. If your water is not properly balanced, it will become "hungry" for minerals and may leach plasticizers from your vinyl liner, making it brittle.

1. Total Alkalinity (TA): Adjust to 80–120 ppm. This acts as a buffer for your pH.
2. pH Levels: Aim for 7.2 to 7.6. A slightly higher pH (7.6) is acceptable as it helps prevent acidity-related corrosion during the winter.
3. Calcium Hardness: Ensure a minimum of 200 ppm. Low calcium in above ground pools can lead to liner staining.
4. Sequestering Agent: Add a metal-out product to prevent iron or copper from precipitating out of the water as it cools.

Warning: Never add chlorine shock and algaecide at the same time. High chlorine levels can neutralize the active ingredients in the algaecide. Add the shock first, wait 24 hours, and then add the winter algaecide.

Step 3: Mechanical System Drainage

Water trapped in the pump, filter, or heater will expand by approximately 9% when it freezes, exerting enough pressure to crack cast iron or reinforced plastic housings.

1. Filter Drainage: For sand filters, remove the drain plug at the bottom. Set the multiport valve to "Winterize" or "Closed." For cartridge filters, remove the element, clean it with a degreaser, and store it indoors.
2. Pump Preparation: Remove the drain plugs from the front and side of the pump housing. Disconnect the pump entirely and store it in a climate-controlled area if possible to prevent seal dry-rot and motor corrosion.
3. Heater/Chlorinator: If equipped, drain all internal headers and pressure switches. Blow out the heat exchanger with a shop vac to ensure no pockets of water remain.

Step 4: Water Level Reduction and Line Plugging

Lowering the water level prevents water from entering the skimmer and freezing, which can warp the pool wall.

1. Standard Drainage: Lower the water level to roughly 6 inches below the bottom of the skimmer opening. Do not drain the pool more than 12 inches, as above ground pools rely on the weight of the water to maintain structural integrity against wind and soil pressure.
2. Return Lines: Remove the "eyeball" fittings from the return jets. Insert a rubber expansion plug or a threaded winter plug into the wall fitting.
3. Skimmer Protection: If you do not use a skimmer faceplate cover (like an Aquador), you must disconnect the hose from the bottom of the skimmer to allow any accumulated rainwater to drain out.

Step 5: Air Pillow and Cover Installation

The air pillow serves a mechanical purpose known as "ice compensation." When the surface of the pool freezes, the ice expands inward toward the pillow rather than outward against the pool walls.

1. Inflating the Pillow: Fill the pillow to about 60-80% capacity. Do not over-inflate; the pillow needs "give" to absorb the pressure of the ice.
2. Centering: Tie the pillow in the center of the pool using strings anchored to the uprights. It should stay in the middle to ensure even pressure distribution.
3. The Cover: Pull the winter cover over the pool and the air pillow. Thread the cable through the grommets and use the winch to tighten it securely around the pool perimeter.

Pro-Tip: If you live in a high-wind area, use "winter cover clips" that snap onto the top rail. These prevent wind from getting under the cover and creating a "parachute effect" that can tear the grommets or pull the cover into the water.

Comparison of Winterization Methods and Materials

The following table compares the two primary methods of above ground pool closing: the Traditional Drain-Down and the Skimmer-Plate (Aquador) method.

Common Winterization Failures and Field Fixes

Understanding the root causes of winter failures allows for proactive prevention. Most issues stem from mechanical oversights or chemical imbalances.

• Scenario: The Air Pillow Dislodges or Deflates

  
  
  
  • Root Cause: Improper anchoring or over-inflation causing the seams to burst during a freeze.
  • Actionable Fix: Use a "velcro" patch kit for minor leaks or replace the pillow. To prevent shifting, use a four-point tie-down system rather than a two-point system, ensuring the strings have enough slack to move as the cover fluctuates with water weight.

• Scenario: The Cover Sinks into the Pool

  
  
  
  • Root Cause: Accumulation of excessive rain or melt-water on top of the cover, or a hole in the cover allowing pool water to seep through.
  • Actionable Fix: Use a submersible cover pump to remove water as it accumulates. If the cover is torn, use a vinyl cover patch kit immediately. Do not attempt to lift a cover heavy with water, as this can damage the pool’s top rails.

• Scenario: Cracked Filter Tank or Pump Housing

  
  
  
  • Root Cause: Failure to remove the drain plugs or a "vacuum lock" that kept water inside the internal components.
  • Actionable Fix: Always leave drain plugs off for the winter (stored in the pump basket) to allow for air circulation. If a crack occurs, the component usually requires replacement, as high-pressure pool systems cannot be reliably repaired with epoxy.

• Scenario: Green Water Upon Opening (Even After Closing Clear)

  
  
  
  • Root Cause: Closing the pool while the water was too warm (above 65°F) or using a mesh cover that allowed UV light and fine debris to enter.
  • Actionable Fix: Ensure the use of a solid winter cover that blocks 100% of UV light. If a mesh cover is used, you must add an extra dose of algaecide in early spring, about a month before the actual opening.

Frequently Asked Questions

Do I need to use pool antifreeze in my above ground pool?

In most above ground pool configurations, antifreeze is unnecessary because the plumbing lines are disconnected and drained rather than buried underground. However, if you have a hard-plumbed system with PVC pipes that cannot be easily moved, you should use non-toxic, propylene glycol-based pool antifreeze to protect the lines.

Can I close my pool without an air pillow?

It is not recommended. In freezing climates, the air pillow is the only thing preventing a solid sheet of ice from exerting lateral pressure on your pool walls. Without a pillow, the expanding ice can buckle the steel wall or pop the liner out of the track, leading to a total structural failure.

How often should I check the pool during the winter?

You should inspect the pool at least once a month. Check the tension of the cover cable, ensure the air pillow is still centered, and use a cover pump to remove any standing water. Monitoring these elements prevents small issues from becoming expensive repairs in the spring.

Should I keep the filter running until the day I close the pool?

Yes. You should maintain full filtration and sanitation right up until the moment you begin the winterization process. Stopping filtration early allows contaminants to build up, which makes the chemical winterization kit less effective and increases the likelihood of algae growth.

Secure Your Investment for the Spring

Properly winterizing your above ground pool is the most effective way to extend the lifespan of your liner and mechanical equipment. Following these technical steps ensures that when the temperatures rise, your pool will be ready for a seamless, crystal-clear opening with minimal effort.