Once your pool water drops to around 10°C (50°F), it’s time to close up for the season — and getting the steps right now can save you hundreds of dollars in spring repairs. A pool closed incorrectly, especially one where water is left sitting in the pump, filter, or plumbing lines, is one of the most common causes of cracked equipment and burst pipes when a Canadian winter sets in. Here’s a step-by-step guide to closing your pool properly before the frost arrives.
Why Timing and Technique Matter
Freezing water expands, and it doesn’t care whether it’s expanding inside your garden hose or inside a $600 pool filter. Any water left behind in equipment or plumbing over the winter can crack housings, split pipes, and damage tile lines — damage that often isn’t obvious until you try to reopen the pool in spring. Most Canadian pool professionals recommend closing once water temperature is consistently below 10°C, and you can safely wait until mid-November in milder regions (sources: Beneva, Co-operators).
Step 1: Give the Pool a Final Deep Clean
Skim, brush, and vacuum the pool thoroughly before you do anything else. Removing leaves, algae, and debris now prevents staining and bacterial growth from taking hold under the cover all winter.
Step 2: Test and Balance the Water Chemistry
Use a test kit to check pH, alkalinity, and calcium hardness, and adjust each to the manufacturer’s recommended range. Balanced water protects your liner and equipment from scaling or corrosion over the winter months (source: iA Financial Group).
Step 3: Shock the Water and Add Winterizing Algaecide
Shock the pool to kill off bacteria, then add a winterizing algaecide formulated for long-term dormancy. This combination is what keeps the water from turning green under the cover — a much easier fix now than a full spring algae bloom cleanup.
Step 4: Lower the Water Level
Drain the water to roughly 15–20 cm (about 6 inches) below the skimmer inlet on vinyl-liner pools, or below the tile line on gunite pools. This keeps water out of the skimmer body and prevents ice from cracking it (sources: Pool Supplies Canada, Leslie’s Pool Supplies). Don’t drain below this level — pools are designed to have water in them, and fully emptying an inground pool can cause the structure to shift or the liner to collapse.
Step 5: Drain and Blow Out the Equipment
Drain all water from the pump, filter, heater, and chlorinator, along with any attached hoses. For inground pools, blow out the underground plumbing lines with a shop vac or small air compressor to force out any remaining water, then plug the lines. Add pool-specific, non-toxic antifreeze to the lines and skimmer for extra protection — never use automotive antifreeze, which is toxic and not designed for this purpose (source: In The Swim). A general guideline is about one gallon of pool antifreeze per 10 feet of pipe.
Step 6: Protect the Skimmer
Place a skimmer plug or “gizzmo” winterizer into the skimmer opening. These foam or expandable devices absorb the pressure of ice forming inside, protecting the skimmer body from cracking — a small, inexpensive part that prevents an expensive repair.
Step 7: Remove Loose Accessories
Take out ladders, diving boards, baskets, and any other removable fittings. Clean and store them somewhere dry so they aren’t damaged by ice, snow, or freeze-thaw cycles over the winter.
Step 8: Cover and Secure the Pool
Install a proper winter pool cover and secure it tightly with water bags, cables, or clips, depending on your pool type. A snug cover keeps out leaves and debris and reduces the amount of spring cleanup you’ll need to do before reopening.
A Few Things to Double-Check
Before you walk away for the season, confirm the pump and filter are completely drained, the cover is secure against wind, and — if you have a saltwater system or heat pump — that you’ve followed the manufacturer’s specific winterizing instructions, since these components sometimes need extra steps beyond a standard closing.
Closing a pool is one of those jobs that rewards patience: rushing through the water-chemistry or line-draining steps is exactly how homeowners end up with a burst pipe or a green swamp come May. Give yourself an afternoon, work through the steps in order, and your pool will be ready for an easy reopening once the weather turns warm again.
Sources: beneva.ca, cooperators.ca, ia.ca, poolsuppliescanada.ca, lesliespool.com, intheswim.com
