How To Close My Above Ground Pool: Step-by-Step Winterization Guide

Properly winterizing an above ground pool requires systematically balancing water chemistry, protecting the structural integrity of the vinyl liner against ice expansion, and completely draining all pump and filtration components. Executing these steps before ambient temperatures drop below freezing prevents severe frame collapse, costly liner tears, and off-season algae infestation. Following precise chemical and operational parameters guarantees an effortless opening when warmer weather returns.

Pre-Winterization Checklist & Planning Benchmarks

Closing an above ground pool is a critical preventative maintenance protocol that safeguards your investment against freezing temperatures, structural collapse, and heavy debris load. Timing is vital: closing too early while ambient daily temperatures remain above 65°F (18°C) creates an ideal environment for algae spores to consume your winterizing chemicals long before spring arrives. Wait until outdoor temperatures consistently remain under 65°F before beginning this process.

Essential Gear, Tools, and Materials

• Winter Chemical Kit: Non-chlorine or calcium hypochlorite shock, non-foaming polyquat 60 algaecide, and a stain-and-scale sequestering agent.
• Physical Protection Gear: Heavy-gauge winter cover, cable and winch tightening assembly, cover clips or shrink wrap, and an air pillow (ice equalizer).
• Equipment Plugs & Seals: Skimmer faceplate plate/plug (e.g., Aquador) or expandable freeze plug, and threaded return jet plugs with rubber O-rings.
• Maintenance Hardware: Submersible cover pump, pool brush, telescoping pole, manual vacuum setup, and shop vacuum or leaf blower for blowing out lines.

Mandatory Prerequisite Standards

• Chemical Balance Targets: pH range of 7.2–7.6, Total Alkalinity (TA) between 80–120 ppm, Calcium Hardness (CH) between 175–225 ppm, and Free Chlorine at 1.0–3.0 ppm prior to shocking.
• Structural Assessment: Inspection of top rails, uprights, vinyl liner, and wall joints for rust, strain, or leaks prior to cover installation.

Duration and Labor Benchmarks

• Active Labor: 3 to 5 hours across a two-day timeframe (allowing chemical circulation periods).
• Estimated Materials Budget: $120 – $275 depending on pool volume and cover rating.

Step-by-Step Above Ground Pool Closing Workflow

Step 1: Deep Clean and Vacuum the Pool Interior

• Remove all floating accessories, solar covers, ladders, and skimmer baskets. Clean steps and ladders thoroughly with a non-abrasive vinyl cleaner before storing them.
• Skim the surface to clear floating leaves, insects, and organic detritus.
• Brush the walls, floor, and vinyl seams to loosen microscopic algae and biofilm.
• Vacuum the pool floor using a manual vacuum connected to the skimmer. If heavy organic debris is present, vacuum directly to waste if your filter valve setup permits. Leftover organic matter consumes winter algaecide and creates permanent stains on vinyl liners over months of contact.

Pro-Tip: Pay special attention to the area right along the waterline. Apply a vinyl-safe degreaser or tile cleaner to eliminate oil rings before lowering the water level, preventing bath oils and sunscreen residues from hardening onto the liner.

Step 2: Adjust Chemistry and Add Winterizing Chemicals

1. Test pool water using a reliable liquid reagent test kit or digital scanner.
2. Adjust Total Alkalinity to 80–120 ppm first, as TA buffers pH fluctuation. Use sodium bicarbonate to raise TA or muriatic acid to lower it.
3. Adjust pH to 7.2–7.6. Maintaining proper pH prevents acidic corrosion of steel pool walls and prevents scale deposits from bonding to the liner.
4. Adjust Calcium Hardness to 175–225 ppm. Low calcium levels force the water to leech minerals from vinyl stabilizers, shortening liner lifespan.
5. Add a sequestering agent (stain and scale inhibitor) according to package dosing instructions based on total gallonage. Allow it to circulate for at least 4 hours.
6. Shock the pool using calcium hypochlorite or non-chlorine shock (potassium monopersulfate) to elevate chlorine levels to 5–10 ppm, eliminating latent bacteria and organic contaminants.
7. Run the pump continuously for 8 to 12 hours to distribute all chemicals uniformly across the water matrix.
8. Add a non-foaming winter algaecide (preferably Polyquat 60). Pour it evenly around the perimeter while the pump is running.

Warning: Never add winter shock and algaecide simultaneously. High chlorine concentrations destroy the active polymers in algaecides. Add shock first, run the filter for a full cycle, and add algaecide only after chlorine levels drop back below 3.0 ppm.

Step 3: Adjust Water Level or Install Skimmer Seals

• Option A (Traditional Draining Method): Drain the water level 4 to 6 inches below the bottom of the skimmer faceplate and return jet fitting using a submersible pump or backwash hose. Do not lower the water level more than 6 inches below the skimmer; over-draining deprives the pool walls of hydrostatic pressure, risking frame collapse under heavy winter wind.
• Option B (Skimmer Seal Method): Install a freeze-proof skimmer faceplate cover (such as an Aquador) directly over the skimmer opening inside the pool. This allows you to keep the pool water at normal operating height, offering maximum structural strength against winter winds and eliminating the need to drain thousands of gallons of water.

Step 4: Winterize Plumbing, Pump, and Filtration Systems

1. Disconnect flexible PVC or corrugated hoses from the skimmer, return fitting, pump, and filter. Drain all residual water from hoses, roll them flat, and store them indoors.
2. Remove the drain plug at the bottom of the pump strainer pot. Turn the pump housing upside down to clear all trapped water, then store the motor assembly in a climate-controlled, dry location.
3. Drain the filtration tank:
   
   
   • Sand Filters: Unscrew the bottom drain plug and let the tank drain completely (this may take hours). Set the multiport valve lever to the "Winterize" or "Closed/Special" position to prevent gasket compression and allow internal air flow.
   • Cartridge Filters: Remove the drain plug, open the top manual air relief valve, unlock the locking ring, and extract the filter elements. Clean the elements with a filter soak solution, dry thoroughly, and store them indoors.
   • DE Filters: Drain the tank, remove and hose down the grid assembly, discard old DE powder, and leave the drain plug off over the winter.
4. Install a rubber freeze plug with an expanding wingnut into the return jet wall fitting from the inside of the pool to block water entry.
5. Screw a Gizzmo (or an empty, weighted plastic milk jug) into the bottom threaded hole of the skimmer housing to absorb ice expansion if water enters the skimmer body.

Warning: Leaving trapped water inside a pump, sand filter valve, or rigid line will lead to catastrophic freeze cracking. Water expands approximately 9% when freezing, generating pressures high enough to split heavy-duty cast plastic housings.

Step 5: Position and Anchor the Ice Equalizer Air Pillow

• Inflate a heavy-gauge air pillow to 60% to 70% of its maximum capacity. Do not over-inflate; the pillow must have sufficient give to absorb the inward pressure of expanding surface ice.
• Center the pillow in the middle of the pool.
• Tie synthetic ropes to the corner grommets of the pillow and anchor them to opposite top rails of the pool frame. The pillow must remain dead-center so that ice expands inward toward the pillow rather than outward against the pool walls.

Pro-Tip: Place a piece of duct tape or patch kit over the air pillow inflation valve after sealing it. Temperature drops cause pressure changes that can pop open unreinforced air valves during mid-winter freezes.

Step 6: Install and Secure the Winter Cover

1. Drape the winter cover across the pool, unfolding it carefully over the centered air pillow. Ensure the cover rests flat on the surface of the water without excessive tension pulling down on the top rails.
2. Feed the coated steel winter cable through every metal grommet along the outer overhang perimeter of the cover.
3. Thread the ends of the cable into the hand winch (turnbuckle). Crank the winch until the cable draws taut under the bottom lip of the top rail caps, sealing the cover tightly against the outer pool wall.
4. Apply wall clips or wrap 4–6 tight layers of commercial pool winter wrap (heavy plastic film) around the exterior wall where the cover edge meets the top rail frame. This prevents wind from getting underneath the cover, which can billow and rip the tarp or tear pool walls during winter storms.
5. Place 2–3 inches of water on top of the cover using a garden hose to weight it down initially and prevent whipping in strong winds.

Technical Specs & Chemical Parameters for Winterization

Common Off-Season Pool Failures & Field Fixes

Cover Sinks Below Water Surface

• Root Cause: Heavy rain or melted snow accumulation creates excessive downward weight, or an unaddressed leak in the air pillow drops center support, causing edges to slip through the winch system.
• Actionable Fix: Instantly deploy an automatic submersible cover pump to clear top deck water. Loosen the winch slightly, pull the cover outer edges taut to restore proper overhang perimeter, re-tighten the winch, and add 4–5 extra layers of winter cover wrap around the top rail border to lock it down.

Wall Buckling or Structural Rail Creep

• Root Cause: The water level was lowered too far beneath the skimmer line (greater than 6–8 inches), removing internal hydrostatic counter-pressure. Heavy freezing soil or strong winds then push the unsupported metal wall inward.
• Actionable Fix: Immediately refill water to 4–6 inches below the skimmer line using a hose slid carefully beneath the cover. Inspect the interior frame for creased steel panels or displaced uprights before full spring fill.

Water Turns Green/Black Upon Spring Opening

• Root Cause: The pool was closed too early while water temperatures were above 65°F, chlorine shock neutralized the algaecide due to improper chemical sequence timing, or the winter cover had light-permeable tears.
• Actionable Fix: Double shock the pool water with liquid chlorine (sodium hypochlorite) immediately upon lifting the cover in spring. Run the filter continuously for 48 hours while maintaining free chlorine above 10 ppm, backwashing/cleaning filter media every 12 hours until clear.

Split Pump Housing or Cracked Multiport Valve

• Root Cause: Residual water remained trapped in lower housing pockets due to missing drain plug removal or leaving the selector handle in the "Filter" position.
• Actionable Fix: In-field plastic welds rarely withstand 15–30 PSI operating pressure. Replace the cracked pump strainer pot or valve housing casting. Prevent future failure by storing wet equipment components indoors and using non-toxic RV antifreeze inside plumbing lines if lines cannot be removed.

Frequently Asked Questions

When is the absolute best time to close an above ground pool?

Close your above ground pool only after ambient outdoor daily high temperatures consistently stay below 65°F (18°C). Closing while the weather is still warm allows algae to rapidly consume chlorine and algaecide, causing heavy blooms under the cover before winter even begins.

Do I need to completely drain my above ground pool for winter?

No, never drain an above ground pool completely. Vinyl-lined pools rely on the weight of the water (hydrostatic pressure) to hold the liner smooth against the sand bed and support the structural integrity of the steel frame; draining completely will cause the walls to collapse under wind loads or the liner to shrink and ruin.

What size air pillow do I need, and how tight should it be?

Select an air pillow that covers roughly 10% to 20% of your pool's total surface area (typically a 4x4 foot or 4x8 foot pillow for standard round or oval pools). Inflate it to only 60–70% capacity so it can compress without popping when water freezes and expands around it.

Can I use household bleach instead of pool closing shock?

While household bleach contains sodium hypochlorite, it has a lower concentration of active chlorine than pool-grade liquid shock and often contains additives or fragrances that damage vinyl liners. Use dedicated pool-grade calcium hypochlorite granular shock or 10–12.5% pool-grade liquid chlorine for winterization.

How do I keep strong winter winds from tearing my pool cover off?

Tighten the cover cable secure with a ratcheting winch, then apply wall clips along the top rails. Wrap the entire exterior perimeter where the cover hangs over the wall using 4 to 6 continuous layers of heavy plastic pool winter wrap to seal out wind entry underneath the cover edge.

Secure Your Pool for the Off-Season

Following a methodical closing routine protects your above ground pool hardware, preserves your vinyl liner, and saves you hundreds of dollars in repair costs every spring. Take the time to execute chemical adjustments, freeze-proofing, and cover security accurately to guarantee a crystal-clear pool opening next season.