The Correct Way to Close Your Pool for Winter: How to Keep Your Pool Clear in Spring

If you properly winterize your pool, you’ll be able to open it clear in the spring. The good news is, you don’t need to hire an expensive company to do it for you. In this guide, I’ll walk you through the necessary supplies and steps for closing your pool (both inground and above-ground). You can watch the video below or continue reading. But first, let's address an important question…

When is the best time to close your pool for winter?

The ideal time to close your pool is when the outdoor temperature consistently falls below 65°F (18°C). Cooler temperatures inhibit algae growth, helping your water remain clear during the offseason.

What if temperatures occasionally rise above 65°F (18°C) during the winter?

If you experience several warm days in the offseason, you can balance your pool’s water chemistry on those days to keep it clean until reopening.

Essential Supplies for Winterizing Your Pool

The supplies you need will depend on your local climate, the accessories in your pool, and whether you've kept your water chemistry balanced leading up to the closing. Having everything ready beforehand will save you from last-minute trips to the store.

Here’s what you’ll need:

• A winter pool cover or safety cover
• Water tubes (if you don't have a spring-secured safety cover)
• Rubber expansion plugs to block water in the plumbing lines
• A Gizzmo or skimmer plate to protect the skimmer from freezing
• Air pillow (for above-ground pools)
• An air compressor (for inground pools) to clear the plumbing lines
• Shop vac (wet/dry) to remove standing water around the pool
• Submersible pump to lower the water level
• pH Increaser/Decreaser
• Alkalinity Increaser or baking soda
• Polyquat 60% algaecide (non-copper)
• Chlorine shock
• Metal sequestrant (metal remover) to prevent stains

Step-by-Step Pool Winterization

1. Thoroughly Clean Your Pool

Use a pool brush to scrub the walls and floor, especially in the corners and hard-to-reach areas. This dislodges sediment and any algae spores. Afterward, vacuum all the debris that gets stirred up. If your pool shows signs of algae, use a special algae brush (for concrete pools) to remove it.

Important: Don’t close your pool while the water is green! This will make reopening it in the spring far more difficult.

2. Test and Balance the Water

Before closing, it’s essential to test your water and make sure it’s balanced. You can use test strips, a test kit, or take a sample to a pool store. Properly balanced water prevents corrosion and scale buildup during the winter.

Here are the ideal levels:

• pH: 7.2 – 7.8
• Alkalinity: 80 – 120 ppm
• Chlorine: 1 – 3 ppm

Make sure chlorine levels are below 5 ppm; too much chlorine can interfere with other chemicals.

3. Shock Your Pool

Shock your pool with chlorine the night before or a few days before you close it. Run the pump overnight to circulate the chlorine. It’s best to shock at night to avoid chlorine breakdown due to sunlight. I recommend using calcium hypochlorite or dichlor shock rather than liquid chlorine because it’s easier to manage.

4. Add Winterizing Chemicals

Add polyquat 60% algaecide to prevent algae from forming over the winter. If your pool cover has a mesh section that lets in debris, consider using a double dose.

If your pool water contains high levels of metals (common with well water), add a metal sequestrant to prevent staining.

5. Clean the Filter and Pump

Thoroughly clean your pool filter and pump to remove debris and bacteria. This will help avoid unpleasant surprises when reopening in the spring.

For cartridge filters, remove and wash the cartridge. For sand filters, backwash it. For D.E. filters, clean them as you would clean a sand filter.

Once cleaned, drain all water from the pump, filter, and heater if applicable.

6. Lower the Water Level (Optional)

Lowering the pool water level is optional and depends on your situation. You can install a winter cover plate on your skimmer to avoid draining your pool. If you prefer, lower the water by 3-4 inches below the skimmer to prevent freezing and cracking.

Make sure to place a Gizzmo or empty bottle in the skimmer to act as an ice compensator.

7. Blow Out the Plumbing Lines (Inground Pools)

For those living in colder climates, it’s crucial to blow out your pool’s plumbing lines to avoid freezing and cracking. If you’re unfamiliar with this process, consider hiring a professional.

Blowing out lines involves:

• Removing return fittings and skimmer baskets
• Setting your multiport valve to recirculate
• Using an air compressor to blow air through the plumbing system

If you’re not confident in doing this, it’s better to call in an expert to avoid damage.

8. Remove Pool Accessories

Remove ladders, rails, and other accessories from the pool to prevent damage from winter chemicals and rusting. Store them in a cool, dry place.

Don’t forget to remove return fittings and clean your skimmer baskets as well.

9. Install a Pool Cover

You have two main options for pool covers: regular winter covers and safety covers. Winter covers keep debris out of the pool, while safety covers prevent animals or people from accidentally falling in.

Regardless of the type, use a pool cover pump to prevent water from pooling on top of the cover. Check the cover periodically throughout the winter.

Final Thoughts

Winterizing your pool can seem like a big task, but it’s manageable with the right tools and knowledge. If you’re uncertain about any part of the process—especially blowing out the lines—it’s worth hiring a pro to ensure the job is done right. Proper winterization prevents costly damage and makes opening your pool in the spring much easier.