Pool Closing Checklist: 5 Must-Have Winterizing Items

As the summer heat fades and the first crisp autumn breeze ripples across the water, the reality of seasonal maintenance sets in. Closing a backyard pool is not merely a chore; it is an investment in protecting a major recreational asset. Choosing the right winterization gear now is the difference between a seamless spring opening and a multi-thousand-dollar repair project.

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Why Proper Winterization Prevents Costly Spring Repairs

Water is one of the few substances on earth that expands as it freezes, increasing in volume by approximately nine percent. In a backyard pool, this expansion exerts immense force on everything it touches, from plastic skimmer wells to underground PVC plumbing lines. Without proper winterization, expanding ice can easily crack structural components and split pipes, leading to underground leaks that are incredibly expensive to locate and repair.

Beyond structural damage, stagnant winter water is a breeding ground for aggressive algae and staining minerals. If a pool is left uncovered or chemically untreated, organic debris will rot over the winter, permanently staining vinyl liners or plaster finishes. Spending a few hundred dollars on high-quality winterizing gear prevents these catastrophic failures, ensuring the pool is structurally sound and easy to clean when warm weather returns.

Safety Cover – Loop-Loc Mesh Safety Pool Cover

An open pool is a year-round safety hazard, especially during the off-season when no one is actively monitoring the backyard. The primary job of a safety cover is to prevent accidental submersions by children, pets, and wild animals, while simultaneously keeping out heavy debris like branches and leaves. Unlike cheap tarps, a true safety cover is anchored directly into the deck, creating a taut barrier that can support immense weight.

The Loop-Loc Mesh Safety Pool Cover is the industry gold standard for this level of protection. Built with super-dense mesh, it allows rain and melted snow to drain through into the pool so water never pools on top, while blocking out fine debris and a significant portion of algae-promoting sunlight. The brass anchors sit flush with the pool deck when not in use, preserving the clean look of the outdoor living space.

• Material: Ultra-strong polypropylene mesh
• Weight Capacity: Designed to support the weight of an adult elephant
• Anchoring System: Solid brass anchors and heavy-duty stainless steel springs
• Warranty: 15-year pro-rated warranty

Before purchasing, accurate measurements of the pool’s exact shape and step locations are critical, as a loose safety cover cannot support weight safely. This cover is perfect for homeowners with concrete or paver decks who prioritize maximum safety and minimal off-season maintenance. It is not suitable for above-ground pools or setups without at least three feet of solid decking around the perimeter to secure the anchors.

Cover Pump – Little Giant APCP-1700 Cover Pump

For pool owners who choose solid winter covers instead of mesh, standing water is a constant threat. Rain and melting snow collect on top of the cover, creating heavy pools that strain the cover material, pull anchors loose, and attract breeding mosquitoes. A dedicated cover pump sits directly on the cover to automatically evacuate this water before it can cause structural damage.

The Little Giant APCP-1700 Cover Pump is engineered specifically to handle this harsh, debris-filled environment. It features an integrated mechanical float switch that automatically activates the pump when water reaches two inches deep and shuts it off when the level drops to half an inch. The wide, weighted base keeps the pump upright on the vinyl, preventing it from tipping over and running dry.

• Flow Rate: Up to 1,745 gallons per hour
• Cord Length: 25-foot heavy-duty power cord
• Discharge Connection: Standard 3/4-inch garden hose thread
• Debris Screen: Removable intake screen for easy cleaning

Keep in mind that this pump requires a reliable, active outdoor GFCI outlet throughout the winter to function automatically. It also requires occasional monitoring during freezing spells, as the pump must be brought indoors if the temperature drops low enough to freeze the water inside the housing. This pump is an absolute necessity for anyone using a solid safety cover or a standard tarp cover, but it is unnecessary for those with free-draining mesh covers.

Winterizing Kit – In The Swim Ultimate Winter Kit

Placing a cover over balanced water is only half the battle; the water must also be chemically treated to resist algae growth and mineral staining over a six-month period. A comprehensive winterizing kit provides pre-measured chemical doses designed to slowly dissolve and protect the water column during the cold dormant months. This prevents the dreaded “green spring opening” that ruins filters and wastes hundreds of dollars in startup chemicals.

The In The Swim Ultimate Winter Kit provides a multi-stage chemical defense system that is incredibly easy to deploy. It includes a powerful, slow-dissolving non-chlorine winter shock, a concentrated algaecide, a stain-and-scale protectant, and a unique winter floating dispenser. This float slowly releases carbon-based sanitizing agents into the water long after the pump has been turned off for the season.

• Treatment Capacity: Available in kits for pools up to 35,000 gallons
• Kit Contents: Winterizing powder, algaecide, stain preventer, and a winter floater
• Chemical Compatibility: Safe for both plaster and vinyl-liner pools
• Storage Life: Sealed chemicals can be stored for the following season if unused

For the best results, these chemicals must be added to the pool after the water temperature drops below 60 degrees Fahrenheit, as algae growth slows down significantly at lower temperatures. It is important to run the filtration system for at least four hours after adding the chemicals to distribute them evenly before draining the water level. This kit is ideal for pool owners looking for an all-in-one chemical solution, though it is not a replacement for balancing pH and alkalinity beforehand.

Air Pillow – Swimline Vinyl Pool Cover Air Pillow

Above-ground pools face a unique threat from freezing water. As a thick sheet of ice forms across the pool surface, it expands outward, pushing directly against the delicate metal walls of the pool. An air pillow placed beneath the cover acts as an expansion cushion, collapsing under the pressure of the ice and absorbing the destructive outward force before it can ruin the pool walls.

The Swimline Vinyl Pool Cover Air Pillow is a rugged, heavy-gauge vinyl cushion designed to survive extreme sub-zero temperatures. Measuring 4×4 feet, this pillow creates a high point in the center of the pool, which also helps push rainwater and debris toward the outer edges of the cover for easier removal. The reinforced corner grommets allow for secure tethering to the pool sides.

• Material Thickness: Heavy-duty 16-gauge vinyl
• Dimensions: 4 x 4 feet (standard size)
• Inflation Valve: Leak-proof push-in valve
• Attachment Points: Four corner grommets for centering ropes

The most common mistake with air pillows is inflating them to 100 percent capacity; they must only be filled to 60 to 80 percent capacity to allow room for compression when the ice expands. If inflated fully, the cold air inside will expand, causing the seams to pop under the first heavy freeze. This accessory is mandatory for all above-ground pool owners, but it is generally unnecessary for in-ground pools where the surrounding earth absorbs the expansion forces.

Expansion Plug – Swimline Rubber Winterizing Plug

Once the plumbing lines of an in-ground pool are cleared of water, they must be sealed air-tight to prevent water from creeping back in and freezing. Expansion plugs slide into the returns, cleaner lines, and skimmer ports, expanding to create a watertight seal when tightened. Without these plugs, the vacuum created inside the blown-out plumbing will slowly pull water back into the lines.

The Swimline Rubber Winterizing Plug features premium, heavy-duty rubber that maintains its elasticity even in deep-freeze conditions. The large nylon wing nut allows for easy tightening without the need for specialized tools, and it will not rust or seize over the winter like cheap metal hardware. The tapered design ensures a deep, secure fit in both threaded and non-threaded pipe openings.

• Body Material: Industrial-grade compression rubber
• Hardware: Corrosion-resistant nylon wing nut and stainless steel bolt
• Size Range: Available in sizes from #00 (for small lines) to #14 (for main drains)
• Compatibility: Works on both PVC and copper plumbing connections

Before purchasing, pool owners must measure the exact inside diameter of their return lines, as a mismatched plug size will fail under the pressure of expanding ice. The standard size for most residential pool returns is a #10 plug (1.5 inches), but it is always best to double-check. These plugs are a critical purchase for anyone in a freeze zone closing an in-ground pool, but they are not needed for simple above-ground setups that disconnect their hoses entirely.

Skimmer Guard – Gizzmo Ultra Skimmer Bottle

The skimmer is the most vulnerable component of an in-ground pool during the winter. Because it sits at the water line, water naturally flows into the plastic well, where it can freeze, expand, and crack the skimmer throat—a repair that requires excavating the concrete deck. A skimmer guard acts as a sacrificial expansion chamber, collapsing under ice pressure to protect the outer plastic housing.

The Gizzmo Ultra Skimmer Bottle is a heavy-duty, hollow plastic tube designed to screw directly into the bottom threads of the skimmer well. It features a built-in blowout tube, allowing pool owners to blow out the skimmer line and seal it off without having to lower the pool water level below the skimmer mouth. The thick, molded threads provide a reliable seal that prevents water from leaking down into the plumbing.

• Length: 16 inches (ideal for deep skimmer wells)
• Thread Size: 1.5-inch and 2-inch double-threaded base
• Material: High-density, freeze-tolerant polyethylene
• Design: Collapsible center core for ice pressure absorption

To ensure a watertight seal, apply Teflon tape to the Gizzmo’s threads before screwing it into the skimmer bottom. If the pool has multiple skimmers, a separate Gizzmo is required for each well. This tool is a must-have for in-ground pool owners in cold climates who want to avoid the tedious process of draining their pool water below the skimmer line.

Leaf Net – Blue Wave Rectangular Leaf Net Cover

If a pool is surrounded by deciduous trees, autumn can be a nightmare. Wet, rotting leaves landing on top of a winter cover turn the water on top into a heavy, black sludge that is incredibly difficult to clean off in the spring. A leaf net is a lightweight, loose-weave mesh cover that sits on top of the main winter cover, catching falling leaves so they can be peeled off in one easy motion.

The Blue Wave Rectangular Leaf Net Cover is constructed from exceptionally durable woven polyethylene that resists tearing even when loaded with wet, heavy leaves. The net features a generous four-foot overlap, ensuring it drapes completely over the edges of the pool to catch windblown debris. Once the leaves have finished falling for the season, the net is simply pulled off, leaving the main cover completely clean.

• Material: Heavy-duty UV-protected polyethylene mesh
• Overlap: 4-foot overlap for secure fitment
• Fastening: Heavy-duty ratchet and cable system included
• Weave Density: Tight mesh blocks small leaves while letting water pass

It is vital to remove the leaf net before the first major winter freeze. If the leaves freeze into a solid block of ice on top of the cover, the net cannot be removed without ripping the material. This accessory is a lifesaver for pool owners with heavy tree cover, but it is an unnecessary expense for yards with minimal foliage or only evergreen trees.

Water Chamber – Swimline Double Water Tube

For in-ground pool owners using traditional solid vinyl tarp covers, wind is the greatest enemy. A gust of wind getting under the edge of a loose cover can sail it across the yard, dumping accumulated dirt and freezing water directly into the pool. Water tubes are long, water-filled vinyl chambers placed along the perimeter of the cover to weight the edges down securely against the pool deck.

The Swimline Double Water Tube utilizes a dual-chamber design that prevents the tube from rolling off the cover or down sloping decks. Made from thick, puncture-resistant vinyl, these tubes feature leak-proof valves that seal tightly to prevent water loss over the winter. The double-chamber construction also provides redundancy; if one chamber punctures, the other remains filled to keep the cover weighted down.

• Material: Heavy-gauge vinyl with heat-sealed seams
• Design: Dual-chamber anti-roll construction
• Length Options: Available in 8-foot and 10-foot lengths
• Valve Type: Leak-proof, flush-fit push valves

When filling water tubes, only fill them to 60 to 70 percent capacity to allow room for the water inside to freeze and expand without popping the vinyl seams. Never drag filled water tubes across rough concrete decks, as this can cause pinhole leaks that will slowly drain the tube. These tubes are essential for holding down standard winter tarps, but they are completely unnecessary for pools equipped with anchored safety covers.

How to Safely Blow Out Your Pool Plumbing Lines

Blowing out the plumbing lines is the most critical step in preventing freeze damage to in-ground pool systems. The goal is to evacuate all standing water from the underground PVC pipes and replace it with pressurized air before sealing the lines with plugs. To do this effectively, a high-volume air blower, such as a professional pool blower or a powerful rigid shop vacuum, must be connected to the equipment pad.

Start by setting the pool’s multi-port valve to the “Recirculate” position and removing the drain plugs from the pump and filter. Connect the blower hose to the pump intake or the skimmer line, and turn the machine on to push air through the plumbing system. You will see water bubble violently out of the pool return lines and skimmers; keep the air flowing until only a fine mist or dry air emerges from the ports.

While the air is still actively blowing, quickly insert the expansion plugs into the return lines to lock the water out. Once all lines are plugged, turn off the blower and pour non-toxic propylene glycol pool antifreeze down the lines as an extra layer of insurance. This process prevents any residual condensation from pooling and freezing inside the pipes during extreme winter cold snaps.

Balancing Pool Water Chemistry Before the Hard Freeze

Many pool owners make the mistake of neglecting water chemistry at closing, assuming the cold weather will keep the pool clean. In reality, unbalanced water can etch plaster, ruin pool liners, and cause scale buildup over the winter months. The chemistry must be balanced to the proper parameters at least five to seven days before the final shutdown to ensure the chemicals have time to circulate.

• pH Level: 7.2 to 7.6 (prevents acidic etching of copper and plaster)
• Total Alkalinity: 80 to 120 ppm (buffers the pH and prevents wild fluctuations)
• Calcium Hardness: 200 to 400 ppm (prevents the water from drawing calcium out of plaster)
• Chlorine/Sanitizer: Bring the pool to shock level (approx. 10–12 ppm) and let it drift down slightly before covering

If the pH is allowed to drop too low over the winter, the water becomes highly acidic, which can cause vinyl liners to become brittle and crack. Conversely, high calcium levels combined with freezing temperatures can cause calcium scaling to deposit on the pool walls, leaving a rough white residue that is incredibly difficult to scrub off in the spring. Take the time to test and balance the water thoroughly; your spring self will thank you.

Storing Your Filtration Equipment Safely for Winter

The pool pump, filter, and heater are highly sensitive to freezing temperatures and must be prepped carefully for the winter months. Start by turning off all electrical breakers to the pool equipment pad to prevent accidental startups. Next, locate and remove the drain plugs on the bottom of the pump strainer basket housing, the filter tank, and the pool heater manifold to allow all internal water to drain completely.

Once the filter tank has drained, remove the internal elements for deep cleaning and winter storage. For cartridge filters, remove the polyester elements and hose them down with a filter cleaner spray before storing them in a dry, rodent-free area. For DE (Diatomaceous Earth) filters, backwash the system thoroughly, disassemble the grid assembly, and wash away any remaining DE powder to prevent it from hardening on the grids over the winter.

Finally, place all removed drain plugs, pressure gauges, and small o-rings inside the pump basket and reinstall the pump lid. This keeps all the critical, easily lost components in one designated location so they are easy to find when spring rolls around. If the pump motor is located in an area that experiences extreme sub-zero temperatures, consider disconnecting it entirely and storing it in a basement or heated garage to protect the internal electrical windings.

Properly winterizing a pool is the ultimate form of preventive maintenance for any backyard water enthusiast. By taking the time to secure a high-quality safety cover, blow out the plumbing lines, and chemically balance the water, you protect your investment from the silent, destructive power of freezing winter weather. When the warm spring sun finally returns, you will be rewarded with crystal-clear water and a pool system that is ready to run without expensive delays.