Protecting Your Pool Through an Ontario Winter
For Ontario pool owners, fall closing is one of the two most important maintenance events of the year, alongside opening the pool in spring. Done well, closing protects the plumbing, the liner or surface, and the equipment through the winter, and sets up an easier opening next year. Done poorly, it can mean freeze damage to the plumbing, algae-filled water under the cover, or equipment failures that only turn up once the pool is running again in the spring.
This guide covers the full fall closing process for Toronto and South Mississauga homeowners, with a clear step-by-step checklist and timing guidance for the region. For a broader look at what a professional closing service involves and how to decide between DIY and hiring it out, see our guide to pool closing in Toronto and Mississauga.
When to Close Your Pool in Ontario
The right time to close a pool in Ontario is when water temperatures fall consistently below 15 degrees Celsius. This signals that algae growth has slowed significantly and the risk of freezing is approaching. In Toronto and South Mississauga, including Port Credit, Lakeview, and Clarkson, this typically falls between mid-September and mid-October depending on the year.
Closing too early, while the water is still warm, allows algae to grow under the cover through the fall and creates a more significant problem to deal with in spring. Closing too late risks the water freezing in the plumbing and equipment before winterizing is complete, which can cause serious and expensive damage. Watch the overnight lows more than the calendar date.
Fall Pool Closing Checklist
Step 1: Balance and Treat the Water
- Test all water chemistry parameters and adjust to target ranges
- Shock the pool with a full dose of chlorine shock
- Add a winterizing algaecide and allow it to circulate for several hours before continuing
- Some pool professionals recommend a phosphate remover treatment at closing to reduce algae food sources through winter
Step 2: Clean the Pool Thoroughly
- Brush the walls, floor, and steps
- Vacuum the pool to remove all settled debris
- Empty and clean all skimmer baskets and the pump strainer basket
- Clean or backwash the filter according to the manufacturer’s instructions
Step 3: Remove Accessories
- Remove ladders, handrails, and any steps
- Remove underwater lights if recommended by the manufacturer
- Remove diving boards, slides, water features, and any other equipment
- Clean, dry, and store all removed accessories in a protected location
Step 4: Lower the Water Level
- Lower the water to below the skimmer and return line openings, typically 15 to 30 cm below the tile line
- The exact level depends on the type of cover you are using; a solid safety cover may require a different level than a mesh or standard winter cover
Step 5: Blow Out the Plumbing
- Use a commercial-grade compressor to blow all water out of the plumbing lines, including skimmer lines, return lines, and any dedicated lines for water features or cleaners
- Plug all lines with winterizing plugs immediately after blowing them out
- This step is the most critical for preventing freeze damage. Water left in lines will expand when it freezes and can crack the pipes or fittings
Step 6: Winterize the Equipment
- Drain all water from the pump, filter, heater, and chlorinator
- Remove drain plugs from the pump and filter and store them somewhere they will not be lost
- Add pool antifreeze to skimmer lines if recommended for your system
- Disconnect and store chemical feeders, salt cells, and automation components per manufacturer guidelines
- Cover or protect the equipment from the elements over winter
Step 7: Install the Winter Cover
- Install a clean, well-fitting winter cover that fully covers the pool with no gaps
- Secure the cover properly using water bags, anchors, or cables depending on the cover type
- A properly secured cover stays in place through wind, snow load, and rain. A cover that lifts or shifts during winter lets debris in and undermines the closing
Professional vs. DIY Pool Closing
Many Toronto and South Mississauga pool owners handle their own closing after their first season or two. The process is learnable, and doing it yourself saves a service call each time. That said, closing in particular has steps, especially blowing out the plumbing, that benefit from the right equipment and experience. A frozen plumbing line costs significantly more to repair than the closing service would have cost.
If your pool needs attention beyond routine closing, Destination Pools handles pool restoration across Toronto and South Mississauga. Contact us to discuss what your pool needs.
Frequently Asked Questions
What happens if I close my pool too early in Ontario?
Closing while the water is still warm encourages algae growth under the cover through the fall. You may open in spring to green, heavily contaminated water that takes more time and chemicals to clear. Waiting until water temperatures drop below 15 degrees Celsius before closing reduces this risk.
Do I need to add antifreeze to my pool lines in Ontario?
Pool-specific antifreeze is sometimes used in skimmer lines as an additional precaution, but it is not a substitute for properly blowing out the lines with a compressor. The primary defense against frozen pipes is removing all water from the plumbing before the freeze season begins. Check with your pool professional to see what is recommended for your specific system.
Can I close my pool without draining any water?
Yes. A standard closing only lowers the water level below the skimmer and return openings, it does not drain the pool. Fully draining an inground pool is a separate, more involved process that is not part of routine closing.
What if I skip closing my pool for a year?
An uncovered or improperly winterized pool left through an Ontario winter is exposed to freeze damage in the plumbing and equipment, plus heavy algae growth and debris accumulation in the water. The spring cleanup and any repairs typically cost far more than a proper closing would have.
Should I hire a professional for pool closing in Toronto?
Many experienced pool owners handle their own closing, especially once they are comfortable with the process. If you are new to pool ownership, or if your pool has a complex plumbing configuration, heater, salt cell, or automation system, having a professional handle the first few closings is a worthwhile investment in understanding what the process involves.
