How to Close an Above-Ground Pool

Winterizing your above-ground pool is essential to protect your liner, plumbing, and equipment from freezing temperatures. When done properly, closing your pool saves time, prevents costly damage, and makes spring opening much easier. Follow these professional steps from Mock Pools & Ponds to safely close your above-ground pool for the season. 

Why Pool Closing Is Important 

Cold weather and freezing temperatures can cause major problems if your pool isn’t closed correctly. Water expands when it freezes, which can crack fittings, damage your filter and pump, and tear the pool liner. Proper closing removes debris, balances water chemistry, and safeguards your system until spring. 

Before You Begin 

• Never drain your pool completely. Keep enough water to support the liner and prevent shrinkage or damage. 

• Plan ahead. Choose a mild, dry day before freezing temperatures arrive. 

• Balance your water. Adjust pH, alkalinity, and chlorine levels for long-term protection. 

• Work safely. Wear gloves and eye protection when handling chemicals, and never mix products. 

Pool Closing Tools & Supplies 

• Leaf net, brush, and vacuum or automatic cleaner 

• Pool test kit or bring a sample to Mock Pools & Ponds for free testing 

• Winterizing chemicals: pool shock, algaecide, pH adjusters, and metal control if needed 

• Air blower or shop vac (for clearing lines) 

• Return plug and skimmer plate or winter cover 

• Non-toxic pool antifreeze (for lines, if applicable) 

• Cover clips, cable, and winch system for the winter cover 

Step-by-Step: How to Close an Above-Ground Pool 

1. Clean the Pool Thoroughly

Use a leaf net or skimmer to remove all leaves and debris. Vacuum the bottom of the pool and brush the sides to eliminate dirt and algae. A spotless pool now means far less work when reopening in the spring. 

2. Test and Balance the Water

Before closing, make sure your pool water is properly balanced: 

• pH: 7.2–7.6 

• Total Alkalinity: 80–120 ppm 

• Calcium Hardness: 175–250 ppm 

• Chlorine: 1–3 ppm 

Properly balanced water prevents corrosion, scale buildup, and algae growth over winter. 

3. Add Pool Closing Chemicals

Run your pump and add a winter shock treatment and a non-copper algaecide. Let the system circulate for 6–8 hours to distribute the chemicals evenly. If your pool has metals in the water, add a metal control product to prevent staining. 

4. Lower the Water Level

For most above-ground pools, lower the water to about 2–4 inches below the skimmer opening. This keeps water from entering the skimmer during freezing temperatures but still leaves enough in the pool to protect the liner. 

5. Disconnect and Drain Equipment

• Turn off the pump and filter system. 

• Remove hoses from the skimmer and return fittings. 

• Drain all equipment — including the pump, filter, and chlorinator — completely. 

• Remove drain plugs and store them in the pump basket for next season. 

• If you have a cartridge or DE filter, remove and clean the filter element before storing indoors. 

6. Blow Out and Seal Plumbing Lines (Optional)

If your pool uses hard plumbing, blow air through the lines with a shop vac or blower to remove all water. Add a small amount of non-toxic pool antifreeze to each line and seal with winter plugs. Flexible hose systems can simply be disconnected and drained. 

7. Winterize the Skimmer

Install a skimmer plate or use a skimmer plug to keep water out during the winter. Alternatively, you can add a skimmer gizmo or foam block to absorb expansion if water freezes inside the skimmer. 

8. Remove Accessories

Take out ladders, steps, lights, and solar covers. Rinse, dry, and store all accessories indoors to prevent rust and wear. 

9. Install the Pool Cover

Spread your winter cover evenly across the pool surface. Use cover clips, cable, and a winch to secure it tightly. Make sure the cover sits evenly and isn’t drooping into the water — this helps prevent tearing or sagging under the weight of snow and ice. 

10. Final Check

Ensure all hoses are disconnected, equipment is drained, and the power is off. Double-check that the cover is tight and secure around the entire perimeter. 

After-Closing Tips 

• Check the cover after heavy winds or storms to ensure it remains tight. 

• Remove standing water and debris regularly with a cover pump or leaf net. 

• Inspect cable tension and clips halfway through winter to make adjustments if necessary. 

• Avoid adding chemicals during the off-season. 

Common Mistakes to Avoid 

• Draining the pool too low or completely — it can damage the liner and structure. 

• Leaving water in hoses or the filter system. 

• Skipping the algaecide — it’s critical for preventing green water in spring. 

• Using copper-based algaecides that can stain liners. 

• Failing to secure the cover tightly against winter winds. 

Do you have any other questions regarding closing your above-ground pool in Northeast Ohio? Please call Mock Pools & Ponds at (330) 628-9100, Option #2 for more information!