Master pool care cheat sheet →
❄️Seasonal cheat sheet
Pool Closing Checklist
Winterize step by step, for freeze and mild climates.
Updated · Reviewed by the Skimmer editorial team
When to close
Close when the water stays below about 65°F and the leaves are mostly down. Closing while the water is still warm invites algae under the cover.
Closing timeline
Pool
Climate
Cover
0 of 15 done
1 week out
2 to 3 days out
Closing day
Monthly through winter
Closing water targets
| Reading | Target | Why it matters over winter |
|---|---|---|
| pH | 7.4 to 7.6 | High pH scales surfaces; low pH etches them |
| Total alkalinity | 80 to 120 ppm | Keeps pH from drifting while nobody is testing |
| Calcium hardness | 200 to 400 ppm | Low calcium etches plaster through the winter |
| Free chlorine | Shock to SLAM level, close at 3 to 5 ppm | A clean start keeps algae down under the cover |
| CYA | 30 to 50 ppm | Protects chlorine in mild climates that stay open |
Supply list
- Winterizing kit (shock plus algaecide), or liquid chlorine plus algaecide
- Expansion plugs for each return and line
- Gizzmo or a sealed bottle for the skimmer
- Air pillow and rope (above-ground)
- Pool antifreeze (propylene glycol)
- Shop vac or blower for blowing out lines
- Cover, water bags or anchors
Mistakes to avoid
- Closing too early, while the water is still warm
- Leaving chlorine tabs in the skimmer or floater (they bleach and eat the liner)
- Using automotive antifreeze
- Forgetting to tie off the air pillow so it drifts to the side
- Adding algaecide while chlorine is still high, which wastes it
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General reference for residential pools. Product labels and local guidance override any figure here. See our methodology and editorial policy. Skimmer · skimmer pool care.
Frequently asked
Closing checklist: questions
When should I close my pool?
When the water stays below about 65°F. Below that, algae grows slowly and chlorine lasts.
Should I shock before closing?
Yes, 2 to 3 days before. Then wait for chlorine to drop below 5 ppm before adding algaecide, or the chlorine will break the algaecide down.
How far do I lower the water?
In freeze climates, about 4 to 6 inches below the skimmer for a mesh cover, or just below the returns for a solid cover. Mild climates keep it full.
Do I need pool antifreeze?
Only in freeze climates for lines you cannot fully blow out. Use propylene glycol pool antifreeze, never automotive antifreeze.
Can I close without a winterizing kit?
Yes. Liquid chlorine to shock plus a bottle of algaecide does the same job. The kit is a convenience.
What should I check over winter?
Once a month: water on the cover, the cover anchors, and the water level. In mild climates, also test and top up chlorine.