Niagara winters are no joke. Temperatures drop well below freezing, and any water left in your pool's plumbing lines, pump, or filter will expand when it freezes — cracking pipes, splitting fittings, and causing thousands of dollars in damage. A proper pool closing isn't just about covering the pool; it's about protecting every component of your pool system from the destructive force of freeze-thaw cycles.

Here's the complete guide to closing your pool for winter in Niagara, based on years of experience winterizing pools across Niagara Falls, St. Catharines, Thorold, and the surrounding region.

When to Close Your Pool

Timing matters more than most pool owners realize. Close too early, and warm fall temperatures can turn your winterized pool into an algae farm. Close too late, and you risk an unexpected cold snap freezing your equipment before it's protected.

Period Recommendation
Early September Too early — water is still warm, algae risk is high
Late September Good timing for most Niagara pools
Early–Mid October Ideal — water temps below 15°C, algae growth slows
Late October+ Risky — freeze can come suddenly; book early to avoid scheduling conflicts

The key metric is water temperature, not the calendar. Wait until the water consistently stays below 15°C (59°F). At that temperature, algae growth slows dramatically, and you won't be fighting green water when you open in spring.

Step 1: Balance the Water Chemistry

Before you do anything else, test and balance your water. Balanced water protects your pool surface, plumbing, and equipment during the long winter months.

Target Levels for Closing

  • pH: 7.4–7.6
  • Total Alkalinity: 80–120 ppm
  • Calcium Hardness: 200–400 ppm
  • Chlorine: 1–3 ppm (before adding winterizing chemicals)

Balanced water prevents scale buildup and corrosion during the off-season. If your calcium hardness is low, the water will pull calcium from your plaster or grout, causing etching. If your pH is too high, you'll find scale deposits on your tile line come spring.

Step 2: Clean the Pool Thoroughly

Don't close a dirty pool. Whatever's in the water when you close it will be there — in worse condition — when you open it.

Step 3: Add Winterizing Chemicals

Once the pool is clean and balanced, add winterizing chemicals. These are designed to slowly release over the winter months, keeping algae and bacteria at bay when the water is cold but not frozen.

Standard Winterizing Kit Includes:

  • Winter algaecide (50% concentration, non-copper to avoid staining)
  • Chlorine shock (or non-chlorine shock if you prefer)
  • Stain and scale preventer
  • Enzyme treatment (breaks down organic contaminants over winter)

Run the pump for at least one hour after adding these chemicals to distribute them evenly throughout the pool. Never add chlorine and algaecide at the same time — add chlorine first, let it circulate for an hour, then add algaecide.

Step 4: Lower the Water Level

Lowering the water level is critical for freeze protection. If the water level is too high, water remains in the skimmer and return lines where it can freeze and cause cracking.

How low should the water be? The answer depends on your pool type and cover style:

Step 5: Blow Out and Plug the Plumbing Lines

This is the most important step for freeze protection, and it's where most DIY closings go wrong. Every line that holds water must be cleared and plugged.

  1. Turn off all pool equipment and disconnect power
  2. Use a compressor or shop vac (on blow mode) to push water out of each return line, skimmer line, and main drain line
  3. Watch the return jets until only air comes out — no water spray
  4. Plug each return jet with a threaded winterizing plug
  5. Plug the skimmer line or fill the skimmer with an antifreeze bottle to displace water
  6. For the main drain, blow the line and ensure the water level in the pool pushes back down below the pipe — no plug needed if the line is fully cleared
Critical: Use swimming pool antifreeze (propylene glycol), never automotive antifreeze (ethylene glycol). Automotive antifreeze is toxic and will contaminate your pool water. Pour 1–2 litres into each line after blowing them out for extra protection.

Step 6: Drain and Protect Equipment

Every piece of equipment that holds water must be drained:

Step 7: Remove and Store Accessories

Take out everything that can be damaged by freezing or UV exposure:

Store everything in a dry, protected area. Ladders and rails should be laid flat to prevent warping. Any rubber or plastic components should be kept out of freezing temperatures where possible.

Step 8: Install the Winter Cover

The winter cover is your pool's last line of defense against debris, UV damage, and water contamination. A properly installed cover stays taut and secure all winter.

For Solid Covers (Tarp-Style):

For Safety Covers (Mesh/ solid):

Why Proper Closing Matters

Freeze damage is not covered by most pool warranties. A single cracked return line can cost $800+ to locate and repair. A split pump housing can run $600+. A damaged heater exchanger? $1,500+. The cost of a professional closing is a fraction of what freeze damage costs to repair.

Every year, I open pools that were closed improperly — or not closed at all — and the damage is always worse, and more expensive, than what a proper closing would have cost. The difference between a good closing and a great closing is attention to detail: every line blown, every plug sealed, every piece of equipment drained.

That's what we do at JAYS Pool Service. We close pools the right way — the way that protects your investment through a Niagara winter and has your pool ready to open cleanly and quickly in the spring.