How to Close Your Pool for Winter the Right Way

A pool closed wrong in October turns into a green, algae-choked mess by April, plus a pump or heater that cracked because water sat frozen in the lines all winter. Pool closing isn't complicated, but it has an order of operations, and skipping a step is what turns a one-afternoon job into a spring repair bill. This guide walks through exactly when to start, what to buy, and how to close both above-ground and in-ground pools so they open clean and problem-free next season.

Get the timing and the chemicals right, and pool closing takes an afternoon. Get it wrong, and you're paying for it in March.

Pool Closing Chemicals: What to Buy Before you Start

The chemical step is the one that determines whether your pool opens clear or green. Buy everything before you start draining water, since you'll need to balance and treat the pool before it goes under the cover.

A standard pool closing chemical kit includes:

• Winterizing algaecide: A stronger, longer-lasting dose than what you'd use mid-season, since it has to hold for months without circulation.
• Chlorine-free shock: Oxidizes contaminants without bleaching a vinyl liner or cover over winter
• pH and alkalinity balancers: Get pH to 7.2 to 7.6 and alkalinity to 80 to 120 ppm before closing; unbalanced water corrodes metal fittings and etches plaster over the offseason
• Stain and scale preventer: Stops metals in the water from staining the pool surface while it sits still
• Pool antifreeze (for the plumbing lines, not the pool itself): Non-toxic, pool-safe antifreeze protects any water left in lines after blowout

Test your water first. Adjusting chemistry on a pool that's already balanced wastes product and money. Our full lineup of pool-closing chemicals covers every step above, and you'll find pool-specific antifreeze in our winterizing collection if you're stocking up for the season.

Closing a Pool for Winter: The Step-by-Step Checklist

Closing a pool for winter follows the same core sequence whether it's above-ground or in-ground, with a few differences covered in the next section.

1. Deep clean first. Skim, brush, and vacuum the pool thoroughly. An automatic pool cleaner makes quick work of the pool floor and walls before you drain anything, and it's the last real cleaning the pool gets until spring.

2. Balance the water. Test and adjust pH, alkalinity, and sanitizer levels using the chemicals above.

3. Lower the water level. Drop water below the skimmer for in-ground pools, or follow your specific cover instructions for above-ground pools.

4. Drain and blow out the lines. Use a shop vac or dedicated blower to clear water from pump lines, filter lines, and heater lines. Trapped water expands when it freezes and cracks pipes, pumps, and heater cores.

5. Add pool antifreeze to the lines, not the pool water, wherever water can't be fully cleared.

6. Remove, clean, and store equipment. Pumps, filters, ladders, and skimmer baskets should come out, get cleaned, and get stored somewhere dry and above freezing.

7. Add winterizing chemicals per the product label, then run the pump briefly to circulate before shutting it down for the season.

8. Install the cover and secure it against wind and snow load.

Closing an Above-Ground Pool for Winter

Closing an above-ground pool for winter has a few extra considerations because the structure itself, not just the plumbing, is exposed to weather. Lower the water level to just below the skimmer opening or plug the skimmer entirely, since above-ground skimmers sit closer to the waterline and are more prone to ice damage. Disconnect the pump and filter completely and store them indoors rather than leaving them attached to the pool wall.

For the cover, an air pillow placed in the center of the pool before covering absorbs the expansion from ice forming on top of the water, protecting the pool walls from being pushed inward. This matters more for closing an above-ground pool than an in-ground one, since above-ground walls flex under pressure that a concrete or gunite shell won't.

In-Ground Pool Closing Steps

In-ground pools handle winter weight better structurally, but the plumbing runs longer and often deeper, which means more opportunity for trapped water. Pay close attention to blowing out both the skimmer lines and the main drain line, since main drains sit at the deepest point of the pool and are the easiest section to miss. A mesh cover works for pools in areas with mild winters and lets debris-laden meltwater drain through; a solid cover with a pump on top holds up better where heavy snow accumulates and needs a way to shed weight.

Protecting Pumps, Heaters, and Lines From Freezing

Freeze damage is the single most expensive mistake in pool closing, and it's almost always preventable. Any water left in a pump housing, filter tank, or heater core expands roughly 9% when it freezes, which is enough to crack cast components that cost hundreds of dollars to replace.

• Drain the pump, filter tank, and heater completely, then remove drain plugs and store them somewhere they won't get lost.
• Disconnect and store heaters separately if freezing temperatures are expected for more than a day or two.
• Use a blower on every line, not just the ones you can see water in. Low spots in buried pipe hold water that gravity alone won't clear.
• If the pool has a saltwater system, remove the salt cell for winter storage rather than leaving it in the line.

A dependable set of pool maintenance equipment and water testing supplies makes this step faster and reduces the chance of missing a line.