When should I close my pool for winter?

Close when daytime temperatures stay consistently below 65°F (18°C) but before the first hard freeze. Closing too early wastes chemicals in warm water; closing too late risks freeze damage to plumbing and equipment.

How far do I lower the water to close a pool?

For a mesh cover, lower to just below the skimmer mouth. For a solid cover, about 4–6 inches below the tile line or skimmer. Always follow your specific cover manufacturer manual, since requirements vary.

Do I add shock and algaecide at the same time when closing?

No. Shock first in the evening and circulate overnight. Wait until free chlorine drops below 4 ppm before adding algaecide and stain preventer — high chlorine destroys those products on contact.

Mesh vs solid winter cover — which is better?

Mesh covers drain rain through (less pumping) but admit fine silt and sunlight, so spring cleanup is heavier. Solid covers keep water cleaner but need regular pumping of standing water. Safety covers (mesh or solid) anchor to the deck and support weight — the best protection where children or pets are present.

Should I run my pump during winter?

In freezing climates with a winterized, covered pool: no — equipment is drained and idle. In mild climates where the pool stays open year-round, keep circulating and maintain normal chemistry instead of closing.

Guides / Pool Closing Checklist

Pool Closing Checklist: Winterize Without Damage

Q: Can I use car antifreeze in pool plumbing?

Never. Automotive antifreeze is toxic and not formulated for pool plumbing. Use only non-toxic, pool-safe antifreeze, and only if your equipment manual calls for it — properly blown-out lines usually need none.

Close before the first freeze — usually when daytime highs stay below 65°F (18°C). A proper close prevents cracked plumbing, stained surfaces, and spring algae blooms. Work through the countdown below in order: clean, balance, shock, lower, winterize, cover, and maintain.

Last reviewed: September 23, 2026 by the Pool Calculate Hub experts. Aligns with APSP/NSPF winterization practice and equipment-manufacturer guidance.

The 7-day closing countdown

Do not rush closing into one afternoon. Chemistry needs circulation time, and algaecide added too early is destroyed by shock. Spread the work over several days.

7 days out: deep clean

Brush walls, floor, steps, and behind ladders and lights. Net all debris.
Vacuum slowly and thoroughly. Clean skimmer and pump baskets.
Run the filter 24 hours until the water is clear going into winter.
Backwash sand/DE or rinse cartridges so filtration is at full capacity.

5 days out: balance the water

Test with fresh reagents: alkalinity, pH, calcium hardness, and CYA.
Target: alkalinity 80–120 ppm, pH 7.2–7.6, calcium 200–400 ppm, CYA 30–50 ppm.
Balanced water protects plaster from etching and equipment from corrosion all winter.
Calculate exact doses with our Chemical Calculator.

3 days out: shock in the evening

Shock in the evening per label dose for your volume and circulate overnight.
Size the dose with our Chlorine Calculator.
Do not add algaecide yet — high chlorine destroys it on contact.

1 day out: algaecide and stain preventer

Confirm free chlorine has fallen below 4 ppm before proceeding.
Add winter algaecide and stain/scale sequestrant per label, with circulation running.
For mesh or loose covers, plan a double algaecide dose or a mid-winter top-up under the cover.

Closing day: lower, winterize, cover

Lower the water: mesh cover — just below the skimmer; solid cover — about 6 inches below the tile line. Confirm with your cover manual.
Drain pump, filter, heater, and chlorinator. Remove drain plugs and store them in the pump basket for spring.
Blow out or drain return and skimmer lines; install winterizing plugs and skimmer guards.
Use only pool-safe antifreeze if your manual calls for it — never automotive antifreeze.
Remove ladders, rails, toys, and cleaners; store dry. Place air pillows under solid covers.
Install the cover taut and secure it: cables, clips, springs, or water bags by type.

Cover selection: mesh vs solid vs safety

Cover type	Pros	Cons
Standard mesh	Rain drains through; lightest to handle; lowest pumping effort	Admits silt and light — heavier spring cleanup, more algaecide needed
Solid / tarp	Keeps water cleaner and darker; best algae prevention	Standing water must be pumped regularly; water bags need monitoring
Safety cover (mesh or solid)	Anchors to deck, supports weight; best protection with kids or pets	Highest upfront cost; professional measuring often required

Whichever you choose, water level matters: too high and the cover floods or freezes into the skimmer; too low and hydrostatic pressure risks increase. Follow the manual.

Plumbing blowout: DIY or pro?

Clearing water from underground lines is the single most freeze-critical step. A shop vacuum handles short runs; long or complex plumbing needs a high-volume blower.

DIY with a shop vac or blower: feasible for simple pools with short, accessible lines.
Hire a pro when: lines run long distances, equipment sits below pool level, or you have in-floor cleaning, attached spas, or water features.
Typical pro closing service costs far less than one cracked underground line or pump housing.
After blowout, install winterizing plugs immediately and fit skimmer guards before covering.

Winter maintenance (15 minutes a month)

Pump standing water off solid covers before it deepens and strains seams.
Clear leaves promptly — decaying debris stains covers and feeds spring algae.
Re-tension cables, springs, and water bags after storms and thaws.
Peek under the cover mid-winter: if the water has greened, add algaecide early rather than waiting for spring.

Four closing mistakes that ruin spring

Closing a dirty pool. Debris stains surfaces and feeds algae for months. Clear water in means clearer water out.
Skipping the balance. Acidic water etches plaster; scaling water deposits scale — all winter long.
Adding algaecide with high chlorine. Shock first, wait for chlorine below 4 ppm, then add algaecide and sequestrant.
Forgetting to drain equipment. One freeze cracks housings, grids, and heat exchangers. Pull every drain plug.

In spring, reverse this process with our Pool Opening Checklist.

Frequently asked questions

When should I close my pool?

When daytime highs stay below 65°F (18°C) but before the first hard freeze. Too early wastes chemicals; too late risks freeze damage.

How far do I lower the water?

Mesh cover: just below the skimmer. Solid cover: about 6 inches below the tile line. Always confirm with your cover manual.

Can I use car antifreeze?

Never. Use only non-toxic pool-safe antifreeze, and only if your equipment manual calls for it.

Do I need to run the pump in winter?

Not for a winterized, covered pool in freezing climates. In frost-free climates, keep the pool open and circulating with normal chemistry instead.

Keep going

Chemical Calculator — closing balance doses for your exact volume.
Chlorine Calculator — size the closing shock correctly.
Volume Calculator — confirm gallons before buying winter chemicals.
Pool Opening Checklist — the spring reversal of this guide.
Pool Chemistry Basics — why the balance targets matter.

Print this checklist for closing day.