The Ultimate Professional Guide To Closing An Above Ground Pool For Winter

Successfully winterizing an above ground pool involves stabilizing water chemistry to an LSI-neutral state, evacuating all plumbing to prevent freeze-expansion damage, and installing a tension-secured cover. Key technical benchmarks include maintaining a pH of 7.2–7.6, lowering water levels 4–6 inches below the skimmer return, and utilizing air pillows to displace ice pressure against the pool walls.

Pre-Winterization Assessment and Equipment Inventory

Before initiating the closing process, it is critical to understand the timing of the procedure. Closing too early—while the water temperature remains above 65°F (18°C)—encourages the growth of algae and bacteria, which can consume the winter chemical kit before the first freeze occurs. Conversely, waiting until a hard freeze risks damaging the external plumbing and filter housing. The ideal window is when ambient temperatures consistently drop, but the water remains liquid and manageable.

Mandatory Equipment and Material Checklist

• Water Testing Hardware: A professional-grade DPD (Diethyl-p-phenylenediamine) test kit or digital photometer for accurate Free Chlorine, pH, Total Alkalinity, and Calcium Hardness readings.
• Winter Chemical Kit: Including a concentrated sequestering agent (to prevent metal staining), non-copper-based algaecide, and a non-chlorine oxidizing shock.
• Physical Cleaning Tools: Telescopic pole with a nylon-bristled brush, a leaf vacuum or skimmer net, and a dedicated pool vacuum system.
• Expansion Protection: Heavy-duty vinyl air pillows (typically 4x4 or 4x5 feet) and skimmer expansion plugs or "Gizzmo" style compensators.
• Plumbing Components: Threaded winter plugs for return lines and skimmer faceplate covers (Aquador style) if you prefer not to drain the water below the intake.
• Covering System: A winter cover with a high denier count or weave strength, accompanied by a stainless steel cable and aluminum winch assembly.
• Estimated Duration: 4 to 6 hours of active labor, excluding the time required for chemical circulation.
• Budget Benchmarks: $150 to $400 depending on pool size and the quality of the winter cover selected.

Systematic Winterization: A Seven-Step Execution Protocol

Step 1: Comprehensive Debris Removal and Deep Cleaning

The presence of organic matter—leaves, insects, and pollen—will rapidly deplete your sanitizer levels over the winter months. Use a leaf rake to remove large surface debris, then vacuum the pool floor thoroughly. If the pool has significant sediment, vacuum "to waste" if your multi-port valve allows, which bypasses the filter and prevents clogging during this final clean. Finally, brush the walls and floor to dislodge any microscopic algae spores that may be clinging to the liner.

Step 2: Optimizing the Langelier Saturation Index (LSI)

Water chemistry during the winter is about more than just sanitation; it is about protecting the vinyl liner and metal components from corrosion or scaling. You must balance the water to ensure it is neither "hungry" (corrosive) nor "oversaturated" (scaling).

1. Total Alkalinity: Adjust to 80–120 ppm. This acts as a buffer for your pH.
2. pH Levels: Aim for a narrow window of 7.2 to 7.6. High pH reduces the effectiveness of chlorine, while low pH can cause the liner to become brittle.
3. Calcium Hardness: Maintain 200–400 ppm. Low calcium levels in above ground pools can cause the water to leach minerals from the liner's pigments, leading to premature fading.

Pro-Tip: Always adjust Total Alkalinity before pH, as the former will stabilize the latter, preventing "pH bounce" during the winterization process.

Step 3: Application of Winterizing Chemicals

Once the water is balanced, add your winter chemical sequence. Start with a sequestering agent to prevent mineral precipitation during the cold months. Follow this with a non-chlorine shock to oxidize any remaining organic contaminants. Finally, add a long-life winter algaecide.

Warning: Avoid using "floating" chemical dispensers containing chlorine tablets during the winter. As the water temperature drops, the tablet dissolves slower, but if the floater gets stuck against a wall, the concentrated chlorine can bleach and weaken the vinyl liner, leading to a catastrophic failure.

Step 4: Water Level Reduction and Structural Protection

Standard procedure involves lowering the water level to roughly 4 to 6 inches below the lowest opening (usually the skimmer or the return jet). This prevents water from entering the plumbing where it could freeze and crack the pipes. However, do not drain the pool too low; the weight of the water is what provides the structural integrity of the above ground pool walls against wind and external soil pressure.

• If using a skimmer cover (like an Aquador), you may keep the water at the normal operating level, which provides better support for the winter cover against heavy snow loads.
• Ensure the water level remains at least 12 inches deep in all areas to prevent the liner from shifting.

Step 5: Equipment Evacuation and Storage

Above ground pool pumps and filters are highly susceptible to freeze damage.

1. Pump: Disconnect the pump entirely. Remove the drain plugs from the bottom of the pump strainer housing. Store the pump in a dry, climate-controlled environment such as a garage or basement to protect the internal seals and motor windings.
2. Filter: For sand filters, set the multi-port valve to "Winterize" and remove the drain cap at the base. For cartridge or DE filters, remove the internal elements, clean them thoroughly, and store them indoors.
3. Hoses: Disconnect all flexible corrugated hoses. If you have hard-plumbed PVC, use a shop vacuum to blow air through the lines until you see bubbles in the pool, then quickly plug the lines with threaded winter plugs.

Step 6: Installation of Ice Compensation Air Pillows

Ice expands outward as it freezes. In a confined above ground pool, this lateral pressure can buckle the steel walls. Air pillows (ice compensators) act as a "sacrificial" void. When the ice expands, it compresses the air pillow rather than pushing against the pool frame.

• Inflate the pillow to roughly 60–70% capacity. Do not over-inflate, as the air will expand in the cold and may pop the pillow.
• Center the pillow in the pool using nylon strings tied to the top rails on opposite sides.
• For oval pools, use two or three pillows spaced evenly along the center line.

Step 7: Securing the Winter Cover

Drape the cover over the pool and the air pillow. The cover should be loose enough to rest on the surface of the water but taut enough that wind cannot get underneath it.

1. Thread the cable through the grommets or loops around the entire perimeter.
2. Insert the cable ends into the winch and tighten until the cover is snug against the outer wall.
3. Wall Clips: In high-wind areas, use "cover clips" that snap onto the top rail of the pool to prevent the cover from flapping, which can lead to tearing.

Comparative Specifications for Winterization Components

Common Winterization Failures and Field Fixes

• Scenario: The Air Pillow Shifts to One Side

  
  
  
  • Root Cause: Improper tethering or wind infiltration during the covering process.
  • Actionable Fix: Use a "four-corner" tethering method rather than just two sides. Use a thin nylon cord and ensure there is enough slack for the pillow to move slightly with the water level but not enough to reach the walls.

• Scenario: Cover Sinks Due to Heavy Snow or Rain Accumulation

  
  
  
  • Root Cause: Excessive weight causing the winch cable to slip or the cover material to stretch beyond its tensile limit.
  • Actionable Fix: Use a submersible cover pump to remove standing water regularly. Never allow more than 2 inches of water to accumulate on top of the cover, as this weight can pull the pool walls inward.

• Scenario: Algae Bloom Discovered During Spring Opening

  
  
  
  • Root Cause: Closing the pool when the water was too warm or failing to use a high-quality algaecide.
  • Actionable Fix: Increase the dosage of winter algaecide by 20% if you live in a region with fluctuating winter temperatures. Ensure the cover is "Solid" rather than "Mesh" to completely block the photosynthesis-driving UV rays.

• Scenario: Skimmer Housing Cracks

  
  
  
  • Root Cause: Water remained in the skimmer throat and froze, expanding against the plastic housing.
  • Actionable Fix: Use a "Gizzmo" or a similar foam expansion compensator inside the skimmer. These devices are designed to collapse when ice forms, absorbing the pressure that would otherwise crack the plastic.

Frequently Asked Questions

Should I leave my pool ladder in the water over winter?

No, ladders and steps should always be removed. Not only can they damage the pool liner if they shift under ice, but they also prevent the winter cover from seating properly, which allows debris and sunlight to enter the pool.

How much water should I leave on top of the cover?

You should aim to keep the cover as dry as possible using a cover pump. While a very small amount of water can help "weight" the cover against the wind, excessive accumulation creates a drowning hazard and puts unnecessary stress on the pool’s structure.

Do I need to add chemicals periodically throughout the winter?

If you have a mesh cover, you may need to add a liquid algaecide mid-winter during a thaw, as rain and sunlight can penetrate the mesh. For solid covers that are properly sealed, a single professional-grade winter kit applied at closing is usually sufficient.

Can I use a regular tarp instead of a pool cover?

This is not recommended. Professional pool covers are treated with UV inhibitors and have specific weave strengths designed to withstand the weight of snow and ice. A standard tarp will likely degrade and tear within weeks, potentially dropping debris and the tarp itself into your pool.

Is it necessary to blow out the lines on an above ground pool?

While above ground pools often have flexible hoses that can be removed, if you have hard-piped PVC lines, you must blow them out using a high-volume air blower or shop vac. Any water trapped in a rigid pipe will expand when frozen and cause a rupture.

Professional Support and Maintenance Resources

Protecting your backyard investment requires precision and the right materials to ensure a seamless transition back to summer use. If you require professional-grade covers or specialized winterization chemicals, consult with a certified pool technician to select products rated for your specific regional climate.