How to close your pool for winter

Closing a pool is mostly about one thing: keeping water from freezing inside your pipes and equipment. Pentair's pump manual puts the stakes plainly: "Freeze damage is not covered under warranty."

Here's the order Hayward, Pentair and Leslie's lay out. There's a printable checklist too.

Live somewhere mild? You might not close at all

If your winters only bring the odd freezing night, you may be able to keep the pool running. Pentair's pump manual says that in mild climates you can run the filter all night to prevent freezing. Hayward's freeze tips say to run every pump whenever it's below freezing, around the clock, until temperatures come back up.

If the power fails during a hard freeze, Hayward's advice is to turn the breakers off, open the filter's air relief and drain the filter, pump and salt cell. If ice has already formed, don't switch the power back on until it melts.

Everyone else, keep reading.

1. Balance the water

Test and adjust a few days before you close. Hayward targets pH 7.2 to 7.8 and alkalinity 80 to 120 ppm; Leslie's uses pH 7.4 to 7.6 with the same alkalinity range. The Pool & Hot Tub Alliance notes that balanced water is less likely to scale or etch surfaces. Use the alkalinity and pH calculators.

2. Shock, then add winter algaecide

Shock the pool so it starts the winter clean. Then wait. Hayward is specific: never add shock and algaecide at the same time. Add winter algaecide only after chlorine has dropped back to 1 to 3 ppm.

3. Clean it

Skim, brush and vacuum. Hayward says to vacuum to waste if there's algae or a lot of debris. Pentair suggests a deep clean and scrubbing the walls. Anything left on the floor spends the whole winter there.

4. Lower the water level

This is where guides disagree, because it depends on your cover and your pool.

Leslie's suggests about 4 to 6 inches below the skimmer for vinyl pools and 4 to 6 inches below the tile line for plaster pools, as long as the lines get blown out and plugged. Hayward says 12 to 18 inches below the skimmer for mesh covers and 3 to 6 inches below the tile for solid floating covers. Pentair says to lower the water but gives no number.

Go with your cover maker's instructions. Leslie's warns against dropping vinyl or fiberglass pools far below the skimmer. And don't drain the pool: River Pools says draining any type of pool is risky, because groundwater can push walls in or lift the floor.

5. Blow out and plug the lines

Blow air through the plumbing from the skimmer, through the equipment and back out the returns, as Hayward describes it, then seal every line with an expansion plug. Put a skimmer guard (often called a Gizzmo) or a plug in each skimmer.

Some owners also add antifreeze to the lines. If you do, use antifreeze labeled for pool plumbing, never automotive antifreeze. Leslie's is clear on that point. Follow the product's label for the amount.

6. Drain the equipment

Pull the drain plugs from the pump and filter and let them empty. Pentair's pump manual says to store the plugs in the pump basket so you can find them in spring. Drain the heater or heat pump and any chlorinator too. Pentair's heat pump manual says its heat exchanger must have all water removed before the first freeze, and Hayward's AquaRite manual says to drain the pump, filter and lines before any freezing weather.

If you cover the pump motor, Pentair warns not to wrap it in plastic or anything airtight.

7. Cover the pool

Fit the cover snugly. Hayward calls mesh safety covers the most desirable and safest option. Solid covers need a cover pump to keep rain and snowmelt from building up on top, which Leslie's says to remove with a pump or siphon.

Over the winter

If you can get to the water, check it about once a month. Pentair and Leslie's both suggest this, and Pentair says to keep chlorine near 3 ppm. Keep the cover clear of standing water and debris.

When spring comes around, the opening guide picks up where this leaves off.