Closing Pool Chemistry for Winter

Before you cover for winter, clean the pool, balance pH and alkalinity, add a closing-appropriate dose of sanitizer or shock per label, and winterize plumbing—cold-climate pools need freeze protection, not just chemicals.

Checklist

• Balance pH
• Adjust alkalinity
• Brush, vacuum, clean filter
• Add chlorine or shock per closing product instructions
• Optional: algaecide if label fits your pool type
• Lower water if required for cover type; blow lines / add antifreeze per local code

Step-by-step sections

1–2 days before cover: get water clear—deal with algae first. Last 24 hours: final balance, shock if needed, circulate, then close per equipment manual.

For ongoing cold-season water sitting, see winter maintenance chemistry.

Common mistakes

• Closing on green water—stains and opens are harder
• Ignoring metal sequestrant needs on fill water with metals
• Skipping freeze protection where pipes burst

Calculators

pH · Alkalinity · Shock · Volume