Pool Closing Guide: Winterizing Your GTA Pool the Right Way
This pool closing guide for Ontario homeowners covers everything you need. Proper pool winterization in Toronto is one of the most important things you can do to protect your investment. Done right, your pool opens easily in spring with minimal damage. Done wrong, freeze damage can cost thousands to repair.
When to Close Your Pool in Ontario
The right time to start winterizing your pool in the GTA is when water temperatures consistently drop below 15 degrees Celsius - typically late September to mid-October. Closing too early wastes the season; closing too late when frost threatens risks freeze damage to plumbing before you have completed winterization.
A common misconception is that pools must be closed on the Thanksgiving weekend. While that is a reasonable target, monitoring your water temperature is more reliable. Many GTA homeowners with pool heaters swim through October and close later in the month.
Why Plumbing Blowout Is Non-Negotiable in Ontario
Ontario's winters regularly reach -20 degrees Celsius or colder. Use this pool closing checklist for the GTA to ensure every step is covered: any water remaining in pool plumbing lines will freeze and expand, cracking PVC pipe, unions, and fittings. A single freeze event can result in $500-$3,000 in plumbing repairs that must be made before the pool can be reopened.
Blowing out the pool lines with a gas-powered air compressor forces all water out of the return lines, skimmer lines, and main drain plumbing. This step is not optional in Ontario - it is the single most important winterization task. Antifreeze (pool-grade propylene glycol) added after the blowout provides additional protection for any residual moisture.
Pool Closing Checklist: Step by Step
Step 1: Final Chemical Balance
Test and balance your water chemistry before closing. Target: pH 7.2-7.4, alkalinity 100-120 ppm, calcium hardness 175-225 ppm. Add a winterizing chemical kit (usually algaecide, stain and scale inhibitor, and a winter floater). Shock the pool 48-72 hours before closing to kill algae. Do not add shocking chemicals and algaecide at the same time - they neutralize each other.
Step 2: Clean the Pool Thoroughly
Vacuum the pool floor, brush the walls, and clean the waterline with a tile and liner cleaner. Remove all leaves and debris from the water. Clean out the skimmer basket and pump strainer basket. A clean pool at closing is far easier to open in spring - algae grows on organic material left in the water over winter.
Step 3: Lower the Water Level
Lower the water level to 30-45 cm below the skimmer opening (for mesh and solid covers) or as directed by your cover manufacturer. Some solid covers with water bags require water level at or just below the return jets. The exact level depends on your cover type.
Step 4: Blow Out All Plumbing Lines
Using a gas air compressor (at least 5 HP), blow out each plumbing line until no water exits the fitting: skimmer lines, main drain line, each return jet, and any feature lines (waterfall, spa jets). Install winterizing plugs in each opening after blowing. Add pool-grade antifreeze to skimmer lines (never automotive antifreeze). Remove the drain plugs from the pump, filter, and heater and store them indoors.
Step 5: Winterize Equipment
Remove the pump lid and drain all water. Remove the filter drain plug and blow out any remaining water. Remove and store the pool heater drain plug. Disconnect and store salt chlorinator cell if applicable. Disconnect the pump motor from power. Remove any above-ground plumbing sections that could hold water and store indoors. Bag and store any removable equipment including ladders, handrails, diving boards, and water features.
Step 6: Install the Winter Cover
Install your winter safety cover or solid cover according to manufacturer instructions. Safety covers should be pulled tight with no sagging areas where water can pool. Solid covers use water bags or cables and anchors to secure. Check that the cover is fully secured before leaving - a loose cover that allows debris to enter the pool will result in a much more difficult spring opening.
Common Pool Closing Mistakes to Avoid
The most expensive mistake when learning how to close a pool in Ontario: not blowing out the lines thoroughly and relying on antifreeze alone. Antifreeze helps but is not a substitute for a proper air blowout in Ontario's severe winters.
Second most common mistake: closing with unbalanced water. Water that is too acidic (low pH) will stain and corrode pool surfaces over winter. Water with low calcium hardness will leach calcium out of concrete and plaster surfaces.
Third: not cleaning the pool thoroughly before covering. Algae, leaves, and debris left in the pool over winter create a much worse problem in spring - green or black water that takes days to treat.
Professional Closing vs DIY
Professional pool closing from Swimpool 360 costs $250-$450 for most GTA pools and includes all of the above steps plus equipment inspection. The peace of mind knowing your plumbing lines have been properly blown out is worth the cost for most homeowners. We also identify equipment issues at closing that can be addressed over winter before the spring rush.
DIY pool closing is feasible for experienced pool owners. The critical requirement is access to a proper gas air compressor for the plumbing blowout - a shop vacuum or small electric compressor does not generate enough pressure to clear all water from buried lines.
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