The deadline isn\'t a date — it\'s the first hard freeze. Close the pool when water temperature stays under 60°F for a week, and at least two weeks before forecast lows hit 32°F. Late closing costs $1,500–$3,000 in cracked plumbing, every time.
Use the calendar as a rough guide and the water temperature as the real trigger. Algae grows aggressively above 60°F; below that, chlorine demand drops and the pool becomes easier to keep balanced through closing.
| Region | Typical close date | Freeze risk |
|---|---|---|
| Upper Midwest, Northeast, Mountain | Mid-September to early October | High by late October |
| Mid-Atlantic, lower Midwest | Mid to late October | Moderate by November |
| Upper South (TN, NC, AR) | Early to mid November | Sporadic, late November |
| Deep South (FL, southern TX, AZ) | Often not closed at all | Rare, regional |
Chemistry first, water level second, plumbing third, cover last.
Brush walls, vacuum the floor, empty skimmer baskets. Debris left in the pool over winter stains plaster and feeds algae.
pH 7.2–7.6, alkalinity 80–120 ppm, calcium hardness 200–400 ppm, free chlorine 1–3 ppm. Run the filter 24 hours after adjusting before moving on.
A heavy chlorine dose oxidizes any remaining organic load. Wait 24 hours and verify chlorine has dropped back near 3 ppm before adding algaecide — adding both at once neutralizes the algaecide.
Algaecide, stain-and-scale preventer, and any kit-specific extras. A pre-mixed winterizing kit handles 90% of pools without overthinking the chemistry.
4–6 inches below the skimmer for inground, 1–3 inches for above-ground. Use a submersible pump or the filter\'s waste setting.
A pool blower (or shop vac on reverse) clears water from skimmer, returns, and main drain plumbing. Plug each return with a winterizing plug as you go. Add pool antifreeze to underground sections in extreme-cold regions.
Drain the pump, filter, and heater per manufacturer instructions. Remove the pump basket and store it indoors. Cartridge filter elements come out and get hosed clean before storage.
Ladders, handrails, diving boards, slides, salt cells. Anything that can corrode or freeze comes out and goes inside.
Solid covers need a cover pump on top to drain rainfall. Mesh covers let rain through but require a slightly higher water level. Secure the edges per the cover\'s instructions.
While you\'re thinking about it. Set it for two weeks before you\'ll want to swim — typically mid-April in the Midwest and Northeast, earlier in the South.
Set it for the first week of September if you\'re in the upper Midwest or Northeast, first week of October for the mid-Atlantic, first week of November for the upper South. That gives you 2–4 weeks of margin before the first freeze becomes a real threat.
Closing late is the single most expensive mistake in pool ownership. A cracked pump housing runs $400–800 to replace. Underground plumbing repairs from a freeze can hit $3,000 once the deck has to come up. The reminder costs nothing.
Once closed, set the spring opening reminder right away — see the pool opening checklist for timing. Both reminders together complete the seasonal cycle covered on the main pool maintenance page.
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Late September in northern states, October in the mid-Atlantic and Midwest, November in the upper South. The trigger isn't the calendar — it's when water temperature stays consistently below 60°F for at least a week. Closing earlier wastes swim time; closing later risks a freeze before plumbing is winterized.
A winterizing kit typically includes a chlorine shock, an algaecide rated for low temperatures, a stain-and-scale preventer, and sometimes a pool antifreeze for above-ground plumbing. Brand kits handle most pools fine; the specific chemistry matters less than getting the pool fully balanced before adding any of it.
Balance chemistry to specific winter targets, lower water below the skimmer, blow lines clear and plug them, drain the pump and filter, add winterizing chemicals, remove and store accessories, then install the cover. Plan on 2–3 hours hands-on for an inground pool with a service blower; longer if you're doing it yourself with a shop vac.
For inground pools with a tile line, 4–6 inches below the skimmer mouth — low enough that water won't enter the skimmer and freeze. For above-ground pools, 1–3 inches below the skimmer. Pools with mesh covers or in regions without freezing temperatures don't need to drop the level at all.
Yes, if you're anywhere with a hard freeze. Water left in the underground or skimmer-to-pump plumbing freezes, expands, and cracks the lines or fittings. A pool blower is the right tool; a shop vac on reverse can work for short runs but struggles with long underground plumbing.
A surprise overnight freeze can crack the pump housing, the skimmer, or the underground plumbing — repairs that run $300 for a fitting up to $3,000+ for a full plumbing redo. The damage doesn't always show up until you open in spring and find leaks. Closing on time is the cheapest insurance you'll buy all year.
A closing reminder set in August is the cheapest insurance you'll buy. Cracked plumbing from a late close runs $1,500–$3,000. The email costs nothing.
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