Pool Closing Checklist: Winterize Without Spring Regrets

Every spring-opening horror story was written the previous fall. Close cold, close balanced, get the water out of the pipes, and next year's opening is an afternoon instead of an ordeal.

Step 1: balance the water a week before closing

Winter water sits for months, whatever chemistry you close with is the chemistry doing the fighting until spring. About a week out, test and correct in the standard order (alkalinity → pH → CYA → chlorine, doses via the chemical calculator):

• Alkalinity 80 to 120 ppm, pH at the higher end, 7.6 or so (pH drifts down over winter)
• Calcium 200 to 400 ppm, low calcium water gnaws at plaster all winter
• Free chlorine at the top of normal range; a closing shock 2 to 3 days before covering is standard practice
• Salt pools: no need to change salt, but log the reading so spring dilution is measurable against it (salt calculator handles the top-up math in April)

Step 2: clean like you mean it

Skim, vacuum, brush, and empty every basket. Organic debris under a winter cover is algae food on a slow-release schedule. This is also the right day to deep-clean the filter, a filter stored dirty cakes solid by spring.

Step 3: drop the water level

Lower the water below the skimmer mouth (check your cover and closing method's specific requirement, solid covers and mesh covers differ). Never fully drain, the water's weight protects the shell and liner.

Step 4: get the water out of the plumbing (the step that matters)

In any climate that freezes, water left in pipes is the entire risk: it expands about 9 percent when it freezes and splits PVC, cracks pump housings, and ruptures heater cores. The sequence:

1. Blow out each line (skimmer, returns, main drain) with a shop vac or compressor until it spits air, then plug returns and add a skimmer guard bottle or Gizzmo.
2. Drain the pump, filter, heater, and chlorinator via their drain plugs; store plugs in the pump basket so spring-you can find them.
3. Salt cell: remove, inspect for scale (clean if needed, per the salt guide's maintenance notes), and store indoors.
4. Anything electronic or removable, automatic cleaner, solar cover and reel (store it shaded), thermometers, comes inside.

Step 5: add winter algaecide, then cover

A polyquat winter algaecide (non-metal, non-foaming) is cheap insurance for the shoulder weeks when the water is still 55 to 65°F. Then cover: safety covers anchor to the deck and hold weight; solid tarps need water bags or cable and an air pillow in above-ground pools to relieve ice pressure. A cover that stays sealed all winter is most of the battle, gaps admit light, debris, and spring algae.

Over the winter (10 minutes a month)

• After storms, clear standing water or heavy snow off solid covers with a cover pump or broom.
• Peek monthly: cover sealed, water level not mysteriously dropping (a winter leak shows as a sagging cover, the leak guide applies in April).
• Mild-climate freeze-protection pools: verify the pump's freeze mode actually kicks on the first cold night, not the fifth.