How to winterize your above-ground pool — here's when to start and what to do

1. Clean the pool thoroughly before winterizing

Remove all floating debris, vacuum the pool floor, and brush down the walls to eliminate any algae or mold that could grow during winter months. Use a skimmer net to catch leaves and other surface debris that your vacuum might miss.

For thorough cleaning with less effort, consider using a robot pool cleaner which can handle both floor debris and wall scrubbing automatically.

These devices are particularly helpful for end-of-season cleaning when pools tend to accumulate more leaves and organic matter.

2. Test and balance your water chemistry

Use test strips or a water testing kit to check pH, alkalinity, calcium hardness, and chlorine levels. Your pH should be between 7.4 and 7.6, alkalinity between 100-150 ppm, calcium hardness between 175-225 ppm, and chlorine between 1-3 ppm.

Properly balanced water prevents corrosion of metal components and staining of the pool liner during the months when the pool isn't being actively maintained. You can adjust levels manually with individual chemicals or use a winterizing chemical kit designed for above-ground pools.

3. Shock the pool to eliminate contaminants

Add diluted granular chlorine or non-chlorine pool shock according to package directions, typically one pound per 10,000 gallons of pool water. This treatment removes contaminants that could cause algae growth or staining during winter storage.

Brush the pool floor and walls after adding shock to help distribute the chemicals evenly. Allow the shock treatment to circulate for several hours before proceeding to the next step.

4. Drain and store pool lines and skimmers

Disconnect all pool lines and allow them to drain completely before storing in a dry location away from direct sunlight. Pool lines can crack from freezing water or develop mold if stored while damp.

Remove the skimmer basket and store it indoors for winter. You can either cover the skimmer opening with a winter skimmer cover or monitor it during winter to ensure drainage. Keep the bottom of the skimmer clear so rain water can drain out properly.

5. Winterize your pump and filter system

Run a backwash cycle until water runs clear, then switch to rinse for 30 seconds before moving the valve to the winterize position.

Remove all drain plugs from the pump, filter, chlorinator, and hoses to prevent water from freezing inside the equipment. Store all drain plugs together in the pump basket so you can find them easily next season.

For sand filters, set the multiport valve to winterize and remove the bottom drain plug. Cartridge filters need to be removed, rinsed, and stored indoors with valves left open.

6. Remove and clean all pool accessories

Take out ladders, diving boards, and any other equipment that could be damaged by winter weather or contaminate the pool water if they corrode. Clean all accessories with a pool surface cleaner before storing them indoors in a dry location.

Leaving metal objects in the pool during winter can cause rust and corrosion that stains the liner and creates additional cleanup work in spring. Indoor storage also extends the life of your pool equipment.

7. Install pool pillows and cover

Place a pool pillow under the winter cover if you live in an area with harsh freezing conditions. The pillow breaks up ice sheets that form under the cover, preventing damage to pool walls and the skimmer from ice expansion.

Install your winter cover and secure it with the cable and winch system. If your pool has a deck, add winter cover clips or water bags for extra security. And avoid using bricks, stones, or sharp objects that could damage the liner if they fall into the pool.

When to start winterizing your pool...

Begin winterizing when your pool water temperature drops below 65°F and stays there consistently, typically around mid-October in most regions. Don't winterize too early, as the chemicals won't be as effective if temperatures rise again before winter truly sets in.

The exact timing depends on your local climate, but starting too late risks equipment damage from unexpected freezing temperatures. Monitor weather forecasts and plan to complete winterization before the first hard freeze in your area.