Closing a Swimming Pool: The Complete Winterizing Process

A pool closed correctly in the fall opens up easily and cheaply the following spring. A pool closed carelessly — or too late — often means a green, damaged mess waiting behind the cover. Here's the full process we follow on every closing.

1. Time it right

Closing too early while the pool still gets regular use wastes the effort. Closing too late, after a hard freeze has already hit standing water in the lines, risks cracked pipes and fittings. The general target is once water temperature consistently drops below 65°F.

2. Deep clean before anything else

Skim, brush, and vacuum thoroughly. Anything left in the pool over winter — leaves, algae, debris — breaks down under the cover and makes spring opening far worse. This is the step most worth not rushing.

3. Balance the water one last time

Test and adjust pH, alkalinity, and chlorine before closing. Properly balanced water sits far better over months of dormancy than water that's already drifting out of range going in.

4. Add a winterizing chemical kit

A winter algaecide and stain preventer treatment protects the water while the pool sits unused and unfiltered for months. Skipping this step is one of the most common reasons pools come out of winter green.

5. Lower the water level (if applicable)

Depending on your pool type and cover style, water may need to be lowered below the skimmer and returns to prevent freeze damage to those fixtures. Not every pool needs this — it depends on your specific setup.

6. Blow out the lines and shut down equipment

Water left sitting in pipes, the pump, filter, or heater can freeze and crack them — often the single most expensive mistake of a bad closing. Lines get blown clear, plugged, and equipment is properly powered down and drained.

7. Install the cover properly

A loose or poorly secured cover lets debris and sunlight in over the winter, undoing everything else you just did. A tight, secure fit matters as much as the chemical work that came before it.