How to Winterize an Above Ground Pool

When should you close an above ground pool?

Once the water stays below about 65°F, and colder is better. Algae grows slowly in cold water, so a pool closed while it is still warm gives algae time to grow under the cover. Finish before the first hard freeze, so no water freezes in the pump or filter.

What you need

• A Pool Season closing kit sized to your pool's gallons, 15K or 30K. The sizer on this page does the math.
• A winter cover for your pool size, with its cable and winch.
• An air pillow sized to the pool.
• A skimmer winter plug or cover plate, and plugs for the return fittings.
• A cover pump, if the cover is solid.
• Cover clips, if the yard is windy.

Step 1: Balance and shock the water

Test and adjust a few days ahead. Aim for a pH of 7.4 to 7.6 and total alkalinity of 80 to 120 ppm. Calcium hardness matters less on a vinyl liner; if you follow a range, 180 to 220 ppm is where most guides overlap.

Shock the pool and run the pump for at least 8 hours, one full turnover. Let the chlorine fall to about 1 to 3 ppm before the winter algaecide goes in, because high chlorine can break some algaecides down. Then add the rest of the closing kit exactly as its label says, with the pump running between steps. The label wins over any general guide, this one included, and when your pool falls between kit sizes, round up: a short dose protects less.

Step 2: Clean the pool and the filter

Skim, brush and vacuum on closing day, so nothing sits and rots under the cover. Backwash a sand or DE filter. Take a cartridge out, hose it clean and let it dry completely, so it does not grow mold over the winter.

Step 3: Lower the water, or seal the skimmer

Water left in the skimmer can freeze, expand and crack it. Without a skimmer cover, lower the water about 4 to 6 inches below the skimmer mouth. With a winter skimmer plug or cover plate, you can leave it at the normal level.

Never drain a hard-sided above ground pool. The water holds the walls in shape, and a liner left dry on a warm day can shrink past use. Keep the lowering small, too: most winter covers allow for about 12 inches of lowered water. How far to drain, in detail.

Step 4: Drain and store the pump, filter and hoses

• Power and hoses. Turn the power off. Disconnect the hoses from the pool wall and plug the return and skimmer fittings.
• Pump. Take out its drain plugs and let it empty, then store it indoors, dry. Do not wrap the motor in plastic, which traps condensation.
• Sand filter. Take off the drain cap at the bottom of the tank and leave it off all winter. If the valve has a Winter setting, use it; on a valve without one, Hayward's instruction is to push the handle down and park it between two positions so it drains.
• Cartridge filter. Open the air relief valve, take off the drain cap, and store the clean cartridge dry.
• Heater, chlorinator, salt cell. Open their drain plugs. Store a chlorinator or salt cell indoors.
• Antifreeze. Usually not needed once the hoses are off and the skimmer drains. If the pool is hard-plumbed in PVC, use only non-toxic propylene glycol pool antifreeze in the lines, never in the pump, filter, heater or chlorinator. If you blow out the lines, keep the air under 5 PSI.

Step 5: Take out ladders and pad sharp edges

Remove the ladder, steps, rails and anything else in the water, dry them and store them. Tape or pad any sharp edge on the top rail, deck or fence that the cover could catch on.

Step 6: Float an air pillow in the center

An air pillow takes the push of the ice. As the water freezes, it presses in toward the pillow instead of out against the walls and liner. Fill it about half to three-quarters full, never tight, and tape over the valve. Tie it in the middle of the pool through its grommets to the top rail, not so tight that the strings tear it. Size it to the pool: a 4 x 8 ft pillow suits most 18 to 24 ft rounds. The air pillow size chart has every size.

Step 7: Put on the winter cover

Order the cover by your pool's size, not the cover's. It is cut 3 to 4 ft wider than the pool so it drapes over the top rail: a 24 ft round pool takes a 27 or 28 ft cover. Lay it on the water over the pillow with the overlap even all the way around. Thread the cable through every grommet, run both ends through the winch, and tighten until the cover sits snug under the top rail, so the wind cannot get under it. On a windy yard, add cover clips along the rail.

A solid cover blocks sunlight and fine dirt, so the pool opens cleaner, but rain and snowmelt collect on it and have to be pumped off. A mesh cover drains itself and is lighter, with more cleanup in spring. A leaf net over a solid cover catches falling leaves; take it off before the hard freeze. Winter cover sizes for every pool, and every cover by pool size.

Through the winter

• Pump water off a solid cover once it is more than an inch deep. At 2 to 4 inches it can pull the cover into the pool. Most owners pump once or twice a month.
• Do not break ice or walk on the cover. Let the ice melt, then pump off the water.
• Check the cable tension, and look the cover over for damage once a month.
• In spring, pump off all the water before taking a solid cover off.

Intex and Bestway pools are different

Soft-sided and frame pools are drained and taken down. Intex's manual says to drain, take down and store the pool once temperatures drop below 41°F, because ice can make the liner fail, and Bestway strongly recommends taking its frame pools down for winter. Dry the liner completely, dust it with talc, fold it and store it indoors. The steps above are for hard-sided pools with steel or resin walls.

Mistakes that damage an above ground pool