How To Close An Above Ground Swimming Pool For Winter

Properly closing an above ground swimming pool for winter requires balancing water chemistry, lowering the water table safely below the return jets, and installing a heavy-duty winter cover with an air pillow to absorb ice expansion stress. Executing these steps prevents structural wall buckling, liner cracking, and severe algae blooms that complicate spring startup.

Pre-Operation & Equipment Checklist

Winterizing an above ground pool requires meticulous preparation to protect vulnerable vinyl liners, thin steel or resin walls, and delicate filtration equipment from freeze-thaw cycles. Gathering the right materials before beginning ensures the process is completed before freezing temperatures compromise water balance.

• Essential Gear, Tools, and Materials:

  
  
  
  • Heavy-duty winter cover designed specifically for above ground pools
  • Vinyl-safe winter cover air pillow (plus non-rusting inflation pump)
  • Winch and steel cable (or heavy-duty winter cover clips/ratchet system)
  • Skimmer closure plate (winterizing faceplate) or skimmer Gizzmo plug
  • Thread seal tape (Teflon tape) and pool thread lubricant
  • Bypass kit or winter expansion plugs for return jets and skimmer ports
  • Non-toxic pool antifreeze (propylene glycol-based, rated for plumbing)
  • Heavy-duty pool brush, vacuum hose, and leaf net
  • Winterizing chemical kit (shock, algaecide, metal sequestrant, and slow-dissolving winterizing floaters)
  • Submersible electric utility pump and garden hose
  • Water testing kit (DPD drops or reliable digital test strips)

• Mandatory Prerequisite Knowledge and Standards:

  
  
  
  • Ambient air temperatures must consistently remain below 65°F (18°C) to prevent premature algae growth under the winter cover, but operations must finish before freezing temperatures damage the plumbing lines.
  • Total Alkalinity must be adjusted to 80–120 ppm, pH to 7.4–7.6, Calcium Hardness to 175–225 ppm, and Free Chlorine to 2.0–4.0 ppm prior to adding winterizing chemicals.
  • Never completely drain an above ground pool; the hydrostatic pressure of the remaining water is structurally required to hold the vinyl liner against the pool walls and counter external ground pressure.

• Estimated Budget and Duration Benchmarks:

  
  
  
  • Total time investment: 4 to 6 hours spread across two consecutive days (allowing chemical circulation and water settling time).
  • Financial investment: $100 to $350 depending on whether new covers, winterization kits, and pump replacements are required.

Step-by-Step Winterization Workflow

Step 1: Deep Cleaning and Debris Removal

Begin the closing process at least 48 hours before dropping the water level by thoroughly cleaning the pool interior and exterior perimeter. Brush down all vinyl walls and vacuum the pool floor to remove organic debris, leaves, and sediment that could stain the liner or fuel winter algae growth. Skim the surface to remove floating debris, and clean the pool coping and top ledges.

Pro-Tip: Run your filtration system continuously for 24 hours after cleaning and vacuuming to ensure the water is completely polished and particulate-free before adding winter chemicals.

Step 2: Balancing Water Chemistry and Shocking

Test the water chemistry and adjust the parameters to ideal winter ranges to prevent scale formation, metal corrosion, and algae multiplication. First, balance Total Alkalinity (80-120 ppm), followed by pH (7.4-7.6), and then Calcium Hardness. Next, broadcast a non-chlorine shock or a high dose of granular chlorine (calcium hypochlorite) after sunset to super-chlorinate the water to at least 10.0 ppm, eliminating organic contaminants. Add a broad-spectrum copper-free winter algaecide and a metal sequestrant to prevent staining from dissolved minerals during the off-season. Run the pump for at least six to eight hours to ensure complete chemical dispersal throughout the entire water volume.

Step 3: Lowering the Water Level and Purging Plumbing Lines

Turn off the pump and electrical power breakers to all pool equipment. Attach a garden hose to your submersible utility pump or leverage your sand/DE filter's waste setting to drain the water level. Lower the water level according to your specific skimmer manufacturer's guidelines—typically 3 to 6 inches below the return jet for total winterization, or just 1 to 2 inches below the bottom of the skimmer mouth if you are utilizing a specialized skimmer cover plate. Once the water level is dropped, disconnect the flexible hoses running from the skimmer and return jet to the pump and filter system. Remove the drain plugs from the bottom of the pump, filter tank, and chlorinator to drain all trapped water completely, preventing freeze fractures.

Warning: Never lower the water level more than 6 inches below the return jet in an above ground pool. Draining the pool too much removes the interior water weight needed to counterbalance frozen ground pressure, which can cause the vinyl liner to shrink, pull away from the coping, or cause the pool walls to cave inward.

Step 4: Installing Winter Plugs, Antifreeze, and Air Pillows

Apply Teflon tape to the threads of your threaded winter expansion plugs and thread them tightly into the pool return fittings from the inside of the pool. For extra safety, pour pool antifreeze down the exposed return lines and skimmer throats, then cap the exterior lines. If using a skimmer guard plate, screw it directly onto the skimmer faceplate with a rubber gasket to create a watertight seal. If leaving the skimmer open, insert a hollow plastic Gizzmo plug into the bottom of the skimmer to absorb ice expansion forces. Next, inflate your heavy-duty winter air pillow until it is roughly 60% to 70% full (never overinflate, as cold air contracts and warm air expands) and tie it securely to the center of the pool using nylon rope attached to the top ledges. The air pillow distributes the crushing weight of freezing ice laterally against the pool walls rather than inward.

Step 5: Securing the Winter Cover and Cable Winch

Drape the heavy-duty winter cover evenly over the center air pillow and across the entire pool surface, pulling the excess material down over the outside of the pool wall. Thread the steel cable supplied with the cover through the designated eyelets or loops around the entire perimeter of the cover. Insert the cable ends into the metal winch, pull the cable tight to remove excess slack, and ratchet it closed to lock the cover securely underneath the top rail lip. For high-wind areas, supplement the cable winch by attaching heavy-duty winter cover clips every 2 to 3 feet along the top ledge to prevent wind from getting underneath and tearing the material.

Above Ground Pool Winterization Method Comparison

Common Site Failures and Field Fixes

• Root Cause: The winter cover falls into the pool or sinks below the water surface during heavy snowstorms.
  
  
  • Actionable Fix: Pump accumulated rainwater and melted snow off the top of the cover immediately using a cover pump. Inspect the cable tension, tighten the winch, and replace missing or broken cover clips to re-secure the perimeter.
• Root Cause: The vinyl liner shrinks, pulls out of the coping track, or the pool wall buckles inward over the winter.
  
  
  • Actionable Fix: Never empty the pool completely. If the water level dropped below the safe threshold, refill the pool using a garden hose up to the correct winterizing level immediately upon discovering the drop.
• Root Cause: Green, murky water and severe algae infestation discovered upon spring opening.
  
  
  • Actionable Fix: The winter cover allowed sunlight to penetrate the water, or the winterizing chemical dose was insufficient. Vacuum organic debris to waste, shock the pool with heavy-duty chlorine, run the filter continuously, and use a flocculant or clarifier to drop suspended particles to the floor for vacuuming.
• Root Cause: Cracked return fittings, split PVC pipes, or ruined pump housings due to trapped water freezing.
  
  
  • Actionable Fix: Replace cracked fittings with schedule-40 PVC parts, ensure lines are completely cleared of water in future autumn closures, and add a sufficient volume of non-toxic RV pool antifreeze into all isolated pipe segments.

Frequently Asked Questions

Should I drain my above ground pool completely for the winter?

No, you should never drain an above ground pool completely. The remaining water provides essential structural weight that holds the vinyl liner in place and resists the immense hydrostatic pressure exerted by frozen surrounding soils. Draining the pool entirely risks catastrophic structural wall collapse and irreversible liner shrinkage.

When is the ideal time to close an above ground pool?

The best time to close your pool is in late autumn when water temperatures drop consistently below 65°F (18°C). At this temperature range, bacteria and algae reproduction slows down significantly, allowing your winterizing chemicals to remain effective throughout the entire off-season without degrading prematurely.

Do I really need an air pillow under my winter cover?

Yes, an air pillow is critical for above ground pools because it absorbs the destructive lateral expansion forces of freezing surface ice. Without an air pillow, freezing ice exerts direct pressure outward against the thin steel or resin pool walls, which can warp the frame or split the pool seams.

How do I keep my winter cover from blowing away in high winds?

Ensure the steel cable is ratcheted tightly through the perimeter eyelets using the winch mechanism. Supplement the cable by installing heavy-duty cover clips or wraps every few feet around the top rail, and ensure no excess cover material hangs loosely where wind can catch it.

Can I use regular car antifreeze instead of pool antifreeze?

No, automotive antifreeze (ethylene glycol) is highly toxic, corrosive to pool components, and dangerous to pets, wildlife, and swimmers. You must exclusively use non-toxic, propylene glycol-based pool antifreeze rated specifically for winterizing swimming pool plumbing lines.

Protect your pool investment this off-season by following these technical closing steps to guarantee crystal-clear water and a hassle-free opening next spring. Contact our pool care specialists today for custom winterization kits, replacement liners, and professional maintenance support.