Your Autumn Guide to Professional Pool Closing in Ontario

Sep 2, 2025

What OGS Does, Why It Matters, and How to Prepare for Next Spring

As Ontario heads into cooler nights and earlier sunsets, it’s time to think about closing your pool for winter. A thorough, professional closing protects your investment, prevents freeze damage, and sets you up for an easier, faster opening next spring. At OGS Pool & Spa, we provide full-service pool closing and seasonal maintenance across Whitby, Brooklin, Oshawa, Ajax, Pickering, Durham Region, and the GTA tailored to Canadian winters and local water conditions.

Why a Proper Pool Closing Matters in Ontario

Winter in Southern Ontario brings freeze & thaw cycles, wind, debris, and prolonged periods of inactivity. Without a correct closing, homeowners risk cracked lines, damaged equipment, stained surfaces, algae blooms, and expensive spring cleanups. A professional winterization preserves your water quality, protects plumbing and equipment, and keeps your landscape and hardscape looking pristine all off-season.

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What’s Included in an OGS Professional Pool Closing

Every pool is different, but our closing service follows a proven, step-by-step process designed for Ontario climate and manufacturer best practices:

1) Site prep and water level adjustment

We skim debris, brush as needed, and adjust the water level according to your pool type and cover. Vinyl, fiberglass, and concrete pools may have different recommended draw-down levels to protect skimmers and tile bands.

2) Water testing and balancing

We test and balance pH, total alkalinity, and calcium hardness to winter targets. Proper balance protects interiors from etching, scaling, and staining over the off-season.

3) Shock and winterizing chemicals

We apply an appropriate oxidizing shock and a winter algaecide to start the season with clean, sanitary water. This helps prevent algae growth under the cover and makes spring opening faster and cheaper.

4) Line winterization

We blow out return, skimmer, and main drain lines and add pool-safe antifreeze where required. This is the most critical step to prevent freeze damage!

5) Equipment care

We drain and winterize the pump, filter, heater, and salt cell (if applicable), remove drain plugs, and store components per manufacturer recommendations. For spas and hot tubs, we follow a similar process tailored to your system.

6) Cover installation

We install your safety cover or properly secure your winter tarp and water bags. A tight, well-fitted cover blocks debris and sunlight to discourage algae and protect the water.

7) Final walkthrough

We review off-season tips and provide recommendations for monthly visual checks to ensure your cover and water level remain in good shape through winter storms and thaws.

Do You Drain the Pool for Winter or Leave the Water In?

In almost all residential cases, you do not fully drain a pool for winter in Southern Ontario. Draining completely can cause structural issues, liner shrinkage, hydrostatic pressure problems, and costly damage. Instead, we lower the water level to the recommended height for your pool type and cover system! This protects the skimmer and coping while maintaining the structural stability that the water provides.

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Should You Shock Before Closing?

Yes. A pre-closing shock is a best practice in Canadian climates. Oxidizing contaminants before you cover the pool helps maintain clarity and prevents odours. We also dose a winter algaecide to inhibit growth during mild spells or mid-winter thaws.

What About Spas and Hot Tubs?

If you’re not using your spa over winter, a professional hot tub winterization protects internal plumbing, pumps, and the shell from freeze damage. If you plan to keep it running, we’ll help you set a winter care routine that balances energy use, water chemistry, and safe operation in sub-zero temperatures.

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Common Water-Balance Mistakes (and How to Avoid Them)

Keeping your pool or spa water balanced isn’t just about looks. It protects swimmers, surfaces, and equipment. Here’s where many homeowners struggle:

Skipping regular testing
Water chemistry can swing quickly after heavy rain, heat waves, or high bather loads. Gaps in testing allow problems to compound, leading to cloudy water or algae.

Guessing chemical amounts
Under- or overdosing sanitizer can cause skin and eye irritation, corrosion, or ineffective sanitation. Accurate dosing protects health and hardware.

Ignoring pH and alkalinity
pH and total alkalinity are the foundation of water balance. If they’re off, other chemicals won’t perform as intended, and you risk scale, etching, or liner issues.

Not shocking routinely
Periodic shocking oxidizes organics and helps prevent odour and haze. Skipping this step can leave water dull and unstable, especially in the lead-up to closing.

Pro tip: The simplest way to avoid these mistakes is to use OGS’s Aqua Box subscription or stop by for professional water testing. You’ll get the right products, at the right time, with expert guidance!

Closing Your Pool Doesn’t End the Conversation.

Get ahead for spring! Smart homeowners use the quieter months to plan for next season. Ask us about setting up an Aqua Box for scheduled deliveries through the year, so you open strong in the spring and stay balanced all summer. We can also pre-book your spring opening and discuss upgrades like new covers, energy-efficient pumps, landscape lighting, patio maintenance, or a cabana to extend your outdoor season.

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Why Choose OGS for Pool Closing and Seasonal Maintenance

We understand Ontario winters, local water chemistry, and the demands of Durham Region and GTA properties. Our team brings professional equipment, proven processes, and a preventive mindset to protect your pool, hardscape, and landscaping from winter wear. From pool closings and openings to weekly or biweekly care, we make ownership easier and more enjoyable.

Ready to book your pool closing?

Secure your date now to protect your investment and simplify next spring’s opening. Contact OGS Pool & Spa to schedule your professional pool closing and ask about our Aqua Box subscription and seasonal maintenance plans!

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Begin your landscaping journey with the professional team at OGS Landscape. Fill out our contact form and tell us more about your desired project. Our team will be in touch within two business days to discuss how we can transform your vision for the ultimate backyard retreat into reality.