Learn How to Close Your Inground Pool for Winter

Why You Need to Close Your Pool Before Winter

Closing your inground pool in fall isn't optional—it's the difference between a pool that's ready to go in spring and one that's been damaged by freezing water, ice, and debris. When temperatures drop below 32°F, water expands as it freezes. If water remains in your pool's pipes, equipment, and structure, that expansion can crack concrete, burst pipes, and destroy expensive components like your pump and filter.

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Winter also brings fallen leaves, branches, algae growth, and debris that sit in stagnant water for months. When spring arrives, you're left with a murky, contaminated pool that takes weeks to restore instead of days. Closing properly means draining specific sections, protecting your equipment, and treating the water so it stays balanced during dormancy. The process takes a weekend but saves thousands in damage and repair costs come April.

Your region's climate determines how thorough your closing needs to be. If you live where temperatures consistently drop below freezing—most of the northern United States—you'll need a full winterization. In warmer climates where freezing is rare, you might only need seasonal maintenance. Even if your area rarely freezes, closing still protects against debris, algae blooms, and equipment breakdown from nonuse.

Most pool owners close between mid-September and early November, depending on when the first hard freeze typically arrives in their area. Closing too early leaves your pool exposed to months of fall debris. Closing too late risks a sudden freeze catching your open pool unprepared. Check your local frost date—the average date of the first hard freeze in your region—to time your closing right.

Takeaway: Winterization protects both your pool structure and equipment from freeze damage, prevents debris and algae problems, and makes spring opening much faster and cheaper than dealing with winter damage.

Gather Your Supplies and Tools Before You Start

Before you begin closing, collect everything you'll need in one place. Running back and forth to the store halfway through the process wastes time and money. Most supplies are inexpensive and available at any pool supply store or online. Some items you may already have in your garage. The total cost for closing supplies typically ranges from $150 to $300 depending on your pool size and equipment.

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You'll need chemicals to balance and treat your water before closing. These include pool shock (a large dose of chlorine), alkalinity increaser, pH decreaser or increaser, and an algaecide. Winter-specific chemicals also matter—a pool winterizer treatment prevents algae and bacteria growth during months of inactivity. You'll also need test strips or a liquid test kit to measure your water's current chemistry before making adjustments.

For draining and equipment, gather a submersible pump (if draining below the skimmer), a wet/dry shop vacuum, drain plugs or winterization kits for your equipment, and a compressor or air pump if you're blowing out pipes. You'll need plumbing materials like plugs, caps, and potentially PVC pipe to seal or cover returns and skimmers. Have pipe insulation tape or foam on hand to wrap any exposed plumbing that stays above water.

Basic tools include a socket wrench or adjustable wrench, a screwdriver, a brush for cleaning surfaces, skimmer nets for removing debris, and safety gear like gloves and eye protection. A water level gauge helps monitor how much you've drained. A few tarps or plastic sheeting protect the ground around your pool from spills and keep debris off surrounding areas. Finally, get a pool cover appropriate for your pool type—vinyl, mesh, or solid—and cover fasteners or springs to secure it.

Most pool supply stores offer winterization kits that bundle the main chemicals you need for one pool. These kits cost less than buying items separately and come with instructions. Read your pool's equipment manual before purchasing drain plugs or winterization kits, since different pumps, filters, and heaters use different setups.

Takeaway: Buying all supplies before starting saves time and prevents mid-process shopping trips. A basic winterization kit covers most chemical needs, and equipment-specific plugs and covers vary by your pump and filter type.

Clean, Test, and Balance Your Water

The first step of closing is cleaning your pool thoroughly and balancing its chemistry. This work happens while the pool is still running and circulating water. Start by removing any large debris—leaves, branches, dirt, toys—from the water surface using a net. Brush the pool walls and floor to dislodge algae, dirt, and buildup that's accumulated on surfaces. Pay special attention to corners and the deep end where debris settles.

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Use your pool vacuum to clean the floor. If you have a lot of debris on the bottom, vacuum it to waste (directly out of the pool) rather than back through your filter. This prevents your filter from getting clogged with years of accumulated material right before closing. Run your filter while you vacuum, then run it for a few hours after to ensure the water is clear and particles are removed.

Once the pool is physically clean, test the water chemistry. Use a liquid test kit or strips to measure chlorine level, pH, alkalinity, and calcium hardness. You're looking for specific ranges: chlorine between 1 and 3 ppm (parts per million), pH between 7.2 and 7.6, alkalinity between 80 and 120 ppm, and calcium hardness between 200 and 400 ppm. Record these numbers—you'll need them to know what adjustments to make.

Start by adjusting alkalinity if it's out of range, since pH adjustments work better once alkalinity is correct. If alkalinity is too low, add alkalinity increaser; if too high, add pH decreaser (which lowers alkalinity). Wait a few hours and test again. Next, adjust pH to the 7.2-7.6 range using pH increaser or decreaser as needed. Finally, adjust calcium hardness using a calcium increaser if low. These adjustments take time—don't rush from one chemical to the next in minutes. Space them out by at least a few hours and retest.

Once all levels are in the correct range, add pool shock according to the product instructions. Shock is a high dose of chlorine that kills algae and bacteria before the pool shuts down. Run your filter continuously for 24 hours after shocking. The next day, add an algaecide and the winter chemical treatment (pool winterizer) that prevents green water and algae growth during the off-season. These chemicals work together to keep your water clear and safe even though no one is swimming.

Takeaway: A clean pool with balanced chemistry closes properly and reopens cleaner in spring. Test all levels before adjusting, space chemical additions hours apart, and shock plus winterize before closing the system down.

Drain Your Pool to the Correct Level

Draining sounds simple—just empty the pool—but the correct water level matters for winter safety. You're not draining your pool completely. Instead, you're lowering the water to a level that prevents damage from freezing water pushing against your equipment and structure, while still leaving enough water so the cover doesn't sag into an empty basin.

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For most inground pools with skimmers, drain the water until it's about 18 inches below the skimmer opening. This level is low enough that freezing water in the skimmer won't crack it, but high enough that rain and melting snow won't cause the cover to sag into the pool. For pools with main drains only (no skimmers), drain to about 12 inches below the pool deck. Some pools have both—in that case, the 18-inch mark below the skimmer is your target.

Start by turning off your pump and filter system. Then use a submersible pump to drain water, or use a wet/dry shop vacuum if you have a small amount of water to remove. Connect a pump to a nearby storm drain, sanitary sewer (check local codes—some areas prohibit this), or direct the hose to a downslope area away from your home's foundation. Some municipalities have rules about where pool water can go; a call to your local health department tells you what's allowed in your area.

As you drain, monitor the water level carefully. Lowering too much exposes your pool structure to weather damage and makes it hard to install your cover. Draining unevenly can also cause your pool's