Pool Closing Checklist: How to Winterize Your Pool

Balance Water Chemistry One Final Time

Do a full water test and balance everything before closing. Properly balanced water going into winter resists algae and scale buildup under the cover.

• pH: 7.4–7.6
• Total Alkalinity: 80–120 ppm
• Calcium Hardness: 200–400 ppm
• CYA: 30–50 ppm

Perform a Closing Shock Treatment

Shock the pool with 2 lbs of cal-hypo per 10,000 gallons 24–48 hours before you plan to cover. Add at dusk, run the pump overnight, and let the chlorine drop below 5 ppm before adding algaecide or covering.

Add Winter Algaecide

After chlorine drops below 5 ppm, add a winterizing algaecide according to the bottle directions. This provides slow-release protection through the off-season when the pump isn't running. Don't skip this — it's cheap insurance against a green pool in spring.

Clean the Pool Thoroughly

Brush the entire pool — walls, floor, steps, corners. Vacuum all debris to waste. A clean pool is dramatically easier to maintain over winter. Organic material left in the pool consumes sanitizer and feeds algae under the cover.

Clean and Winterize the Filter

Sand filter: Backwash, then set the multiport valve to "winterize" or "closed." Remove the drain plug from the bottom. Do not add antifreeze to the filter tank.

Cartridge filter: Remove and rinse the cartridge, soak in filter cleaner, allow to dry, and store indoors. Remove drain plugs from the housing.

DE filter: Backwash to remove DE, open the filter, remove and rinse the grids, and store them. Remove drain plugs.

Lower the Water Level

For a mesh safety cover: lower the water 12–18 inches below the skimmer opening. Water can drain through mesh covers, so this level prevents ice damage to the tile line.

For a solid winter cover: lower the water 4–6 inches below the skimmer opening.

Blow Out and Plug the Plumbing Lines

This is the most critical step for freeze protection. Water left in plumbing lines will expand when it freezes and crack pipes, fittings, and equipment.

Use a shop vac on blow mode or a small air compressor to push air through each line from the equipment pad until no more water comes out at the pool end. Then insert expansion plugs (winter plugs) into each return jet and the skimmer throat.

If you're not comfortable doing this yourself, hire a pool professional for the line-blowing step. The cost of a pro closing is far less than repairing split pipes in spring.

Winterize the Pump and Heater

Pump: Remove and store the drain plugs. If the pump is in a freeze zone, consider removing it entirely and storing it in a heated space. Blow out any residual water with compressed air.

Heater: Follow the manufacturer's winterization procedure. Most require removing drain plugs and blowing out the heat exchanger. Gas heaters should have the gas supply turned off at the shutoff valve.

Salt chlorinator: Remove the salt cell, rinse it, and store it indoors. The cell should not stay in the system over winter.

Remove and Store Pool Accessories

Remove ladders, handrails, diving boards, steps, and pool cleaner hoses. Rinse with fresh water, allow to dry, and store indoors or in a garage. Metal parts left outside through winter rust and corrode faster than those stored dry.

Install the Winter Cover

Install the winter cover and secure it properly. For safety covers, use the anchor hardware to pull the cover taut — a loose cover that sags into the pool fills with rainwater and gives algae a breeding ground. For standard covers, use water bags around the perimeter (not cinder blocks — they tear covers). Inflate the air pillow if using one for an above-ground pool.