9 Essential Winterizing Supplies for an In-Ground Pool

Closing down an in-ground pool for the winter is more than just throwing a tarp over the water and hoping for the best. When freezing temperatures arrive, any water left unchecked in your plumbing or pool structure will expand with enough force to crack concrete and rupture PVC lines. Equipping yourself with the right winterizing supplies now ensures that opening day next spring is a celebration rather than a costly construction project.

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Why Proper Winterization Prevents Costly Spring Repairs

Freeze expansion is the ultimate enemy of an in-ground pool. Water expands by roughly nine percent when it turns to ice, exerting thousands of pounds of pressure per square inch on anything trapping it. Without proper winterization, this expansion easily splits underground plumbing lines, cracks skimmer wells, and ruins expensive pump and filter housings.

Beyond structural damage, stagnant winter water invited by poor preparation becomes a breeding ground for algae and invasive organic staining. Cleaning up a green, swampy pool in May requires massive doses of expensive shock, hours of scrubbing, and days of running filtration systems. Spending a little time and money on prevention in the fall saves thousands of dollars in structural repairs and chemical costs when the warm weather returns.

Safety Cover – Loop-Loc Mesh Safety Pool Cover

A safety cover is the primary line of defense protecting an in-ground pool from winter debris, heavy snow loads, and accidental falls. Unlike cheap tarps held down by water bags, a safety cover is anchored directly into the pool deck using heavy-duty springs and brass anchors. This creates a tight, trampoline-like barrier that keeps out leaves and small animals while keeping pets and children safe from water hazards.

The Loop-Loc Mesh Safety Pool Cover is the gold standard for this task because of its legendary “super dense” mesh weave and high break-strength polyester webbing. It allows rainwater and melting snow to drain through slowly so water does not pool on top, while blocking out most sunlight to prevent off-season algae growth. The brass anchors sit completely flush with the pool deck when not in use, ensuring a trip-free zone during the summer months.

When purchasing, precise sizing is non-negotiable; you must measure the exact dimensions of the pool, including any steps, buddy seats, or custom rock features. Installation requires drilling into concrete or wood decks, which means a rotary hammer drill and a steady hand are necessary for the initial setup.

• Ideal for: Homeowners in regions with heavy snowfall who prioritize safety, durability, and a clean pool opening.
• Not ideal for: Above-ground pool owners or those unwilling to drill anchor holes into their surrounding pool deck.

Cover Pump – Little Giant APCP-1700 Cover Pump

Water accumulation is a constant threat to solid pool covers, as rain and melting snow add thousands of pounds of unwanted weight. This weight can stretch safety covers beyond their limits or pull standard tarp covers directly into the pool water. A reliable cover pump automatically removes this water before it can freeze into a destructive, heavy sheet of ice.

The Little Giant APCP-1700 Cover Pump stands out with its automated pressure switch that activates when water levels reach two inches and shuts off when the surface is dry. It moves up to 1,745 gallons per hour, quickly clearing heavy downpours with an energy-efficient, permanent split capacitor motor. The wide, weighted base prevents the pump from tipping over on uneven cover surfaces, while the built-in intake screen resists clogging from leaves.

Buyers should note that this unit requires a standard garden hose connection to redirect the pumped water far away from the pool deck. Regular maintenance is necessary to clear leaves from the intake screen, especially during peak autumn leaf drop.

• Ideal for: Solid cover users and mesh cover owners in high-precipitation zones who need set-it-and-forget-it water management.
• Not ideal for: Deep-freeze climates where the pump is left plugged in and frozen solid in ice without any liquid water to move.

Winter Chemical Kit – In The Swim Deluxe Winter Kit

Pool water left untreated over a long winter will slowly turn into a dark, corrosive, and organic-rich soup. A winter chemical kit delivers a timed-release system of sanitizers and stain preventers designed to work in cold, stagnant water. This ensures that the water remains clear and the pool walls are protected from metal staining and scale buildup for six to eight months.

The In The Swim Deluxe Winter Kit offers a highly effective combination of winterizing powder, non-chlorine shock, stain remover, and a slow-releasing winter sanitizer floater. This multi-stage approach neutralizes contaminants immediately upon closing and continues to fight off microscopic spores throughout the cold months. It contains no harsh copper-based algaecides, protecting vinyl liners and plaster finishes from discoloration.

To maximize the kit’s effectiveness, the chemicals must be dissolved and circulated thoroughly through the pool prior to lowering the water level. The floating canister needs to be weighted and set according to your specific pool volume to avoid localized bleaching.

• Ideal for: Standard pool sizes up to 35,000 gallons looking for a pre-measured, comprehensive winter chemical solution.
• Not ideal for: Small splash pools or spas that require much smaller, custom-dosed chemical adjustments.

Expansion Plug – Anderson Winterizing Plug

Once the plumbing lines are blown out and cleared of water, they must be sealed completely to prevent water from seeping back in. Expansion plugs fit snugly inside return jets and cleaner lines, expanding to create a watertight seal against the pipe walls. Without these, any rising pool water will re-enter the lines, freeze, and crack the underground PVC.

The Anderson Winterizing Plug features heavy-duty, marine-grade rubber and non-corrosive nylon wing nuts that resist degradation from harsh pool chemicals. The ribbed rubber design ensures a multi-point seal that holds up even under the high pressure of freezing ground soils. They are built to withstand seasonal temperature extremes without cracking, shrinking, or losing their elasticity over time.

Ensuring a correct fit requires matching the plug size exactly to your plumbing diameters, which typically range from 1.5 to 2 inches. Users must clean any algae or grit out of the pipe opening before insertion to ensure a perfect, airtight seal.

• Ideal for: Pool owners looking for reliable, reusable line seals that will not slip or rot over winter.
• Not ideal for: Threaded fittings that are better served by specific threaded winter plugs.

Skimmer Guard – Gizzmo Ultra Skimmer Expansion Plug

Skimmer wells are incredibly vulnerable to freeze damage because they sit right at the water line and are surrounded by cold concrete. As ice forms inside the skimmer, it expands outward, easily cracking the plastic housing and causing major underground leaks. A skimmer guard absorbs this expansion pressure, sacrificing itself to save the skimmer body from cracking.

The Gizzmo Ultra Skimmer Expansion Plug is a hollow, heavy-duty plastic tube designed to collapse slightly when ice expands around it. It features a built-in 1.5-inch and 2-inch threaded blowout fitting at the bottom, allowing you to seal the skimmer line and protect the housing simultaneously. This dual-action design keeps water out of the pipes while neutralizing ice pressure inside the well.

Standard Gizzmos may not fit deep-seated commercial or extra-tall skimmers, making the “Ultra” 16-inch version the safer choice for deep wells. Teflon tape should be wrapped around the threads to guarantee an airtight seal when screwing it into the bottom of the skimmer.

• Ideal for: Standard in-ground pool skimmers in climates that experience hard, prolonged winter freezes.
• Not ideal for: Non-threaded skimmer wells or shallow, low-profile above-ground skimmer baskets.

Pool Air Pillow – Robelle Heavy Duty Ice Pillow

When rainwater and snow accumulate on a solid pool cover, they push down on the surface and pull the cover walls inward. An air pillow sits in the center of the water beneath the cover, creating an expansion void. As ice expands across the pool’s surface, it pushes inward against the soft pillow rather than outward against the pool’s delicate tile and walls.

The Robelle Heavy Duty Ice Pillow is constructed from thick, 16-gauge vinyl designed to withstand extreme cold without springing leaks. It features a secure pull-valve that keeps air locked inside, preventing the premature deflation that plagues cheaper pool pillows. The reinforced grommets on the corners allow for easy centering using nylon ropes tied to the pool edge.

For optimal results, only inflate the pillow to about 60 to 80 percent of its capacity. Leaving some slack prevents the expanding ice from popping the pillow like a balloon when winter pressure peaks.

• Ideal for: Pools utilizing solid winter covers or leaf nets in areas prone to thick, surface-ice formation.
• Not ideal for: Tight, highly-tensioned safety mesh covers that do not rest directly on the pool water surface.

Line Blower – Cyclone Pro Commercial Line Blower

Simply draining pool lines by gravity is never enough; pocketed water will always remain in low spots of the underground plumbing. A dedicated line blower uses high-volume, low-pressure air to force every drop of water out of the pipes. This step is the single most critical defense against catastrophic underground pipe bursts.

The Cyclone Pro Commercial Line Blower utilizes a powerful 3.0 horsepower motor that bypasses the limitations of standard shop vacs. It generates up to 130 CFM of air volume, easily pushing water out of deep main drains and long plumbing runs. The rugged polyethylene housing is built for the damp, cold environment of backyard pool pads and features a long-lasting, bypass-cooled motor.

This tool requires a secure connection to the pool plumbing, usually achieved via a quick-connect fitting on the pump strainer basket or skimmer line. Operating it requires careful sequencing of valves to ensure all lines are blown out systematically without burning out the motor.

• Ideal for: DIY pool owners wanting professional-grade winterization and pool service companies looking for a reliable workhorse.
• Not ideal for: Budget-conscious owners with very simple, short plumbing runs who can get by with a high-powered shop vac.

Pool Antifreeze – Splash Non-Toxic Antifreeze

Even after blowing out the plumbing lines, small trickles of water can migrate back down into the pipes due to condensation or minor seal leaks. Pool antifreeze acts as insurance, lowering the freezing point of any residual water to prevent ice formation. It is poured directly into the plumbing lines, skimmers, and pump housings to provide absolute peace of mind.

Splash Non-Toxic Antifreeze is formulated specifically for pool and RV systems, using non-toxic propylene glycol rather than toxic ethylene glycol (automotive antifreeze). It protects plumbing down to -50 degrees Fahrenheit, ensuring lines remain safe during deep winter freezes. Because it is non-toxic, it will not harm swimmers, pets, or pool equipment when the lines are flushed back into the pool in the spring.

This product must be used undiluted; adding water drastically reduces its freeze protection rating. It should never be added directly to the main pool water body, but rather poured directly into cleared plumbing lines before plugging them.

• Ideal for: Pool owners in deep-freeze states who want a failsafe backup for their blown-out plumbing lines.
• Not ideal for: Warm-weather climates where temperatures rarely drop below freezing.

Leaf Net Cover – In The Swim Deluxe Leaf Net

Falling autumn leaves can quickly turn a pool cover into a heavy, rotting mess of organic sludge. Removing wet, decayed leaves in the spring is backbreaking work that often compromises water quality if the debris slips into the pool. A leaf net cover sits on top of your primary winter cover, acting as a lightweight catcher for falling debris.

The In The Swim Deluxe Leaf Net is made of an exceptionally durable, woven polyethylene mesh with a heavy-duty binding. Once the autumn leaves have finished falling, you simply lift the lightweight net off the pool, taking all the debris with it in one swift motion. This leaves your primary winter cover completely clean and free of heavy, rotting organic material for the rest of the winter.

The net should be sized slightly larger than your actual pool dimensions to allow for drape over the cover edges. It must be secured tightly with the included winch and cable system to prevent heavy winds from lifting it.

• Ideal for: Pools surrounded by deciduous trees like oaks, maples, or pines that drop heavy debris in the fall.
• Not ideal for: Pools in open, tree-free areas or those closed late in the season after all leaves have already fallen.

How to Properly Blow Out In-Ground Pool Plumbing

Blowing out the plumbing lines is the most critical technical step in the winterization process. Begin by lowering the pool water level to about three to six inches below the skimmer mouth, or below the return jets if using a solid winter cover. Hook your line blower up to the pump’s drain plug opening or the skimmer line, ensuring a tight seal with threaded adapters or heavy-duty tape.

Turn on the blower and systematically isolate each line using your pool pad valves, forcing air through one line at a time. Start with the return lines farthest from the pump; once you see a steady blast of air and mist shooting out of the jet, quickly slide in an expansion plug and tighten it securely. Repeat this process for each return line, then move on to the cleaner lines and the skimmers.

The main drain at the bottom of the pool requires a slightly different approach known as “air locking.” Blow air through the main drain line until a massive column of bubbles erupts from the bottom of the pool. While the air is actively bubbling, quickly close the main drain valve at the equipment pad to trap the air pocket inside the pipe, preventing water from rising back up.

Crucial Chemistry Adjustments Before Closing the Pool

Closing a pool with unbalanced water chemistry is a recipe for liner degradation, plaster etching, and severe spring algae blooms. Before adding any winter chemicals, the water must be balanced to protect the pool surfaces from the corrosive effects of cold water. Take water samples to a local store or use a reliable test kit to check pH, total alkalinity, and calcium hardness.

Aim to adjust your pH to between 7.2 and 7.6, and ensure your total alkalinity sits comfortably between 80 and 120 ppm. Calcium hardness is especially critical in winter, as cold water is naturally more corrosive; keep it between 200 and 400 ppm to prevent the water from leaching calcium directly out of plaster finishes.

Once the physical parameters are balanced, shock the pool with chlorine several days before putting the cover on. Let the chlorine level drop down to normal operating levels (around 1 to 3 ppm) before adding your winter algaecide and closing kits. This prevents high chlorine levels from breaking down the active ingredients in your winter chemicals, ensuring they remain effective all winter long.

Conclusion

Taking the time to winterize an in-ground pool correctly is the best investment a pool owner can make in their property. By pairing systematic plumbing prep with high-quality safety covers, blowers, and chemicals, the risk of freeze damage is virtually eliminated. When the spring sun finally breaks through, opening the pool will be a simple, stress-free transition back to warm-weather fun.