Learn How to Close Your Inground Pool for Winter

Understanding Why Pool Closing Matters for Winter

Closing your inground pool properly before winter is one of the most important maintenance tasks you can perform as a pool owner. When water freezes, it expands—ice can damage pool walls, pipes, filters, and equipment if the pool isn't prepared correctly. The National Swimming Pool Foundation reports that improper winterization leads to thousands of dollars in repairs annually for pool owners who skip this process or do it incorrectly.

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Temperature matters significantly. When your region's nighttime temperatures consistently drop below 65°F (around 18°C), it's time to begin closing procedures. In northern climates where temperatures reach freezing, closing becomes critical. Even in milder climates where temperatures rarely drop below freezing, closing protects equipment from wear and prevents algae growth during dormant months.

The closing process typically takes one to two days and involves several steps performed in a specific order. Starting too early or too late in the season can create problems. If you close too early, warm weather may cause algae blooms in your covered pool. If you wait too long, you may not finish before the first hard freeze arrives, which can trap equipment in ice.

Different pool types—vinyl-lined, concrete, and fiberglass—require slightly different approaches. A vinyl-lined pool needs protection to prevent damage to the liner, while a concrete pool requires specific drainage to avoid structural damage from ice pressure. Understanding your pool type helps you follow the correct closing procedure.

Practical Takeaway: Mark your calendar for when nighttime temperatures in your area typically drop below 65°F. This is your target window for beginning pool closure preparations. Contact your local pool supply store to confirm the optimal closing timeline for your specific region.

Testing and Balancing Water Chemistry Before Closure

Balanced water chemistry is essential before closing because the pool will sit undisturbed for months. Water that isn't properly balanced can develop algae, staining, and corrosion that causes expensive damage. You should test your pool water for four key components: pH level, alkalinity, calcium hardness, and chlorine.

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The ideal pH level for pool water is between 7.2 and 7.6. Water that's too acidic (pH below 7.2) can corrode metal equipment and damage pool surfaces. Water that's too basic (pH above 7.6) can cause scaling and cloudiness. You can adjust pH using pH increaser (sodium carbonate) or pH decreaser (sodium bisulfate). Test kits cost between $15 and $40 at pool supply stores and provide results within minutes.

Alkalinity acts as a buffer that keeps pH stable. It should measure between 80 and 120 parts per million (ppm). Low alkalinity causes pH to fluctuate wildly, while high alkalinity makes pH difficult to adjust. Alkalinity increaser (sodium bicarbonate) raises alkalinity, while pH decreaser also lowers alkalinity.

Calcium hardness refers to the amount of dissolved calcium in the water. For concrete pools, maintain calcium hardness between 200 and 250 ppm. For vinyl-lined pools, keep it between 150 and 200 ppm. Water with insufficient calcium can damage pool surfaces, while overly hard water causes scaling. Calcium increaser (calcium chloride) raises hardness levels.

Chlorine levels should be between 2 and 4 ppm before closing. Some pool owners use a winterizing chemical kit that includes algaecide, clarifier, and other additives designed specifically for winter storage. These kits typically cost $30 to $60 and are mixed into the water according to package directions.

Practical Takeaway: Purchase a test kit this week and test your water. Write down all four measurements. If any levels are outside the ranges listed above, adjust them according to product instructions. Retest after 24 hours to confirm corrections worked, then proceed with other closing steps.

Cleaning Your Pool and Removing Debris

A clean pool is less likely to develop problems during winter. Debris that sits in water for months can stain surfaces, promote algae growth, and clog filtration systems. Cleaning should happen during the final days before closure, after chemical adjustments are complete.

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Start by skimming the pool surface with a net to remove leaves, insects, and floating debris. Do this daily during the week leading up to closure if your pool is near trees. Use a pool brush to scrub the walls and floor, loosening any algae or buildup. Pay particular attention to corners and steps where debris accumulates. A stainless steel brush works for concrete pools, while softer brushes are needed for vinyl liners to prevent tears.

Vacuum the pool floor using a pool vacuum or robotic cleaner. Manual vacuuming takes 30 to 60 minutes depending on pool size but ensures thorough cleaning. Robotic cleaners cost $400 to $2,000 but provide convenience. Run your filter system continuously during vacuuming to capture debris. Backwash your filter (reverse water flow to clean the filter media) once during this process, and again after vacuuming is complete.

Clean or replace your filter. Filters trap debris and should be in good condition before winter shutdown. Sand filters can be backwashed multiple times before needing replacement, which costs $50 to $100 for sand. Cartridge filters should be removed and rinsed with a hose; if they're more than five years old, consider replacing them ($100 to $300). DE (diatomaceous earth) filters should be backwashed and cleaned; DE powder costs $20 to $40 per bag.

Empty skimmer baskets and any additional strainer baskets. These small containers trap debris and should be clear before winter. Check drains and ensure no debris blocks water flow in any part of your circulation system.

Practical Takeaway: Schedule a full cleaning day. Set aside three to four hours for skimming, brushing, vacuuming, and filter maintenance. If your pool has been neglected, you may need to repeat these steps multiple times. Do final cleaning no more than one or two days before covering the pool.

Draining and Protecting Your Pool Equipment

Water that remains in pipes, filters, and equipment can freeze and cause cracks or damage costing thousands of dollars to repair. The draining process varies by pool type and climate, so follow recommendations specific to your situation.

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For above-ground pools and some inground pools in warmer climates, you may drain the pool completely or partially. For most inground pools, you'll lower the water level below the skimmer but keep water in the pool to protect the structure. Consult your pool manufacturer's instructions or a local pool professional if you're unsure about proper water level for your pool type.

Drain all equipment by opening drain plugs on your filter, pump, heater, and chlorinator. Have a bucket or hose ready to catch water. Some equipment has multiple drain plugs; check your owner's manuals to locate them all. This process takes 30 minutes to one hour and prevents ice from forming inside equipment.

Remove chlorinator cells, salt cell components, and any other removable parts from equipment. Store these in a dry location indoors. These components are sensitive to cold and moisture and may be damaged if left outside.

Disconnect hoses and equipment that will be stored for winter. Pool pumps, filters, and heaters can be disconnected and moved to a garage or storage area. If equipment must stay outside, cover it with a tarp or equipment cover to shield it from snow, ice, and debris. Equipment covers cost $30 to $150 depending on size.

Use antifreeze in your pipes if you live in a climate where temperatures drop well below freezing. Pool antifreeze (not automotive antifreeze, which is toxic) is designed for pool plumbing and costs $15 to $40 per gallon. Pour it into return lines and skimmers according to product instructions to prevent ice blockages.

Practical Takeaway: Gather your pool equipment manuals and locate all drain plugs before you begin. Create a checklist of equipment to drain and drain plugs to open. Take photos of your setup before disconnecting equipment so you remember how to reconnect everything in spring.

Installing and Securing Your Pool Cover

A proper pool cover

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