How to Winterize an Above-Ground Pool

In cold climates, freezing water can crack pumps, split hoses and damage above-ground pool walls. Winterizing takes an afternoon and makes spring opening far easier.

When to close

Close the pool when water temperatures stay below about 65°F (18°C). Closing while the water is warm gives algae a head start under the cover.

What you’ll need

• A winter cover, cover cable and winch
• An air pillow
• Winterizing chemicals (optional algaecide) and shock
• A test kit
• A skimmer plug or cover and return plugs

Step 1: Clean the pool

Skim, brush and vacuum thoroughly. Anything left in the pool will feed algae through winter.

Step 2: Balance the water

Bring alkalinity, pH and calcium into range using our chemistry chart. Balanced water protects the liner and equipment during the months it sits still.

Step 3: Shock

Shock the pool a few days before closing and let chlorine fall back toward normal, so it doesn’t bleach the cover or liner. Our guide to how much shock your pool needs shows the dose. Some owners also add a winter algaecide.

Step 4: Clean the filter

Backwash a sand filter, or remove and clean cartridges. Store cartridges indoors.

Step 5: Lower the water level

Lower the water below the skimmer opening and return jet, following your pool maker’s guidance. Don’t drain the pool completely: above-ground pools need water to keep their shape.

Step 6: Disconnect and drain equipment

Disconnect the hoses, drain the pump, filter and any heater or chlorinator, and store small equipment indoors. Heat pumps and gas heaters drain differently, so follow the manual; our pool heater comparison explains how the types differ. Plug the skimmer and returns.

Step 7: Add an air pillow

Inflate an air pillow and tie it in the centre of the pool. It absorbs the pressure of expanding ice and helps rain and snow run off the cover.

Step 8: Fit the cover

Secure the winter cover with the cable and winch so wind can’t get underneath. Keep the cover clear of heavy snow and pooled water through winter.

When spring comes, our pool opening checklist takes you through the restart.

Frequently asked questions

Do I need to winterize an above-ground pool?

In climates where temperatures drop below freezing, yes. In mild climates, many owners run the pump less and keep the pool balanced instead.

How low should the water be for winter?

Below the skimmer and return fittings, typically a few inches below the skimmer. Follow your manufacturer’s guidance.

What if my air pillow pops?

Replace it if you can, or keep the cover clear of heavy water and snow until spring.