Closing Your Pool for Winter

Quick Answer

Properly winterizing your pool takes 3–6 hours of work and costs $50–100 in supplies. The process: balance chemistry, super-chlorinate, lower the water level, blow out plumbing lines, add antifreeze to lines, remove and store accessories, and install the winter cover. Do this when water temperature consistently stays below 65°F. A proper closing prevents freeze damage, algae blooms, and reduces your spring opening workload dramatically.

What You Need to Know

  • Timing is everything: Close when water temps stay below 65°F. Closing too early (while water is warm) invites algae growth under the cover. In most areas, that’s October–November.
  • Don’t skip the plumbing blowout — a single freeze crack in a pipe or fitting can cost $500–2,000+ to repair.
  • A winter cover is non-negotiable in freezing climates. It keeps debris out, blocks UV (slowing algae), and is a safety barrier.
  • The better your closing, the easier your opening. Pools closed properly can look almost swimmable when opened in spring.
  • Warm-climate pools (no freeze risk) can often stay operational year-round with reduced runtime. This guide focuses on traditional winterizing for freeze climates.
🚨 Freeze Warning: If an unexpected freeze is forecast and you haven’t winterized yet, at minimum run your pump continuously. Moving water freezes at a lower temperature than still water. If you have a freeze protection feature on your automation, make sure it’s enabled.

Deep Dive

Closing Supply Checklist

Gather everything before you start:

Item Purpose Approx. Cost
Winter closing chemical kit Includes shock, algaecide, stain preventer, and sometimes enzyme treatment $25–50
Pool antifreeze (propylene glycol) Protects plumbing lines that can’t be fully blown out $10–15/gallon (need 2–4)
Winterizing plugs Seal return lines after blowout $3–5 each
Skimmer gizzmo or Aquador plate Absorbs ice expansion in skimmer throat $8–15 each
Air pillow (above-ground) Relieves ice pressure on pool walls $15–25
Winter cover or safety cover Keeps debris out, blocks UV, safety barrier $50–200 (tarp) / $1,500–3,500 (safety cover)
Shop vac or air compressor Blowing out plumbing lines Already owned or rent ($40–60/day)

Step 1: Balance and Treat the Water

Do this 1–2 days before the physical closing so chemicals have time to circulate:

Parameter Winter Target Why
pH 7.2–7.6 Prevents scale and surface etching over the dormant period
Total Alkalinity 80–120 ppm Buffers pH drift during winter
Calcium Hardness 200–400 ppm Prevents surface etching in plaster pools
Free Chlorine Shock level (10+ ppm) Super-chlorinate to kill everything before the cover goes on
CYA 30–50 ppm Protects the residual chlorine under the cover

After balancing, add:

  • Shock treatment: A heavy dose — aim for at least 10 ppm FC. This is your last line of defense until spring.
  • Winter algaecide: Use a polyquat-based (non-copper, non-foaming) algaecide rated for winterizing.
  • Metal sequestrant/stain preventer: Prevents metal staining during the months of stagnation.
  • Enzyme treatment (optional): Breaks down organic material that settles under the cover.
💡 Pro Tip: Add shock and algaecide at least 4–6 hours apart. Add the chemicals with the pump running, let them circulate for 24 hours, then do the physical closing steps.

Step 2: Clean the Pool Thoroughly

Any debris or algae left in the pool will only get worse under the cover:

  1. Brush all surfaces — walls, floor, steps, waterline tile, behind ladders.
  2. Vacuum the pool thoroughly. Vacuum to waste if there’s significant debris.
  3. Skim the surface.
  4. Clean the waterline to remove oils and scum that will stain over winter.
  5. Empty and clean all baskets — skimmer, pump, and cleaner.
  6. Clean or backwash the filter one final time. For cartridge filters, do a chemical soak. For DE filters, do a full breakdown and cleaning.

Step 3: Lower the Water Level

The correct water level depends on your cover type:

Cover Type Water Level Notes
Mesh safety cover 12–18″ below tile line Water will rise from rain/snow melt passing through the mesh
Solid safety cover 3–6″ below skimmer mouth Higher level supports the cover; you’ll pump off standing water
Tarp/water bag cover 4–6″ below skimmer mouth Similar to solid covers
⚠️ Warning: Never drain a pool completely for winter. The weight of the water counteracts hydrostatic pressure from groundwater. An empty pool can literally float out of the ground.

Step 4: Blow Out the Plumbing Lines

This is the most critical step for freeze protection. Water left in pipes will freeze, expand, and crack pipes, fittings, or equipment.

What you need:

  • Air compressor (at least 5 CFM) or a powerful shop vac set to blow mode
  • Winterizing plugs for each return fitting
  • Pool antifreeze (propylene glycol — NOT automotive antifreeze)

Procedure:

  1. Turn off the pump and all equipment.
  2. Remove drain plugs from the pump, filter, heater, chlorinator, and any other equipment. Let them gravity drain. Store the drain plugs in the pump basket so you find them in spring.
  3. Set the multiport valve (if applicable) to the “winterize” position, or between two positions to prevent freezing the valve body.
  4. Blow air through each suction line (skimmer lines, main drain) until you see bubbles coming up in the pool. Then quickly plug the line or install a gizzmo.
  5. Blow air through each return line until you see bubbles at the return fitting. Quickly thread in a winterizing plug.
  6. Blow air through the cleaner line, waterfall lines, and any additional plumbing.
  7. Pour 1–2 quarts of pool antifreeze into each skimmer (as extra insurance for the line between skimmer and equipment pad).
  8. Pour antifreeze into any line you couldn’t blow out completely.
💡 Pro Tip: Put the drain plugs, winterizing plugs (extras), and any small removed parts in a zip-lock bag inside the pump basket. When spring comes, everything is in one place.

Step 5: Winterize Equipment

Pump

  • Remove drain plug(s) and let water drain out.
  • If possible, remove the pump and store indoors — this extends the motor and seal life.
  • At minimum, ensure the pump is completely drained and the drain plugs are out.

Filter

  • Cartridge: Remove elements, clean, and store indoors.
  • Sand: Drain the tank. Leave the multiport between two positions or on “winterize.”
  • DE: Drain the tank. Remove grids, clean, store indoors if possible. Leave drain open.

Heater

  • Drain all water from the heat exchanger. Many heaters have specific drain plugs for this.
  • Turn off the gas supply.
  • Cover the top vent to prevent animal entry (use hardware cloth, not solid covers that trap moisture).

Salt Chlorine Generator

  • Remove the cell and store it indoors, clean and dry.
  • Cap or plug the plumbing unions where the cell was removed.
  • See our salt chlorine generator guide for cell storage details.

Automation Controller

  • Switch to “service” or “off” mode — do NOT leave it set to run schedules.
  • If your controller has freeze protection, you may want to leave it active (pump runs when temps drop near freezing) if your area gets intermittent freezes before full winterization.

Step 6: Remove and Store Accessories

  • Ladders and handrails: Remove, clean, store in garage/shed. Protects them from weather damage and makes cover installation easier.
  • Automatic cleaner: Remove, clean, store indoors. Coil hoses loosely to avoid kinks.
  • Pool lights: If removable (niche-mounted), pull them out of the niche and set them on the deck. The cord stays connected — don’t cut it. This protects the light from ice damage in the niche.
  • Eyeball fittings: Already replaced with winterizing plugs in Step 4.
  • Skimmer baskets: Remove and store. Already replaced with gizzmos.

Step 7: Install the Winter Cover

Safety Covers (Mesh or Solid)

  1. Lay the cover over the pool, aligning it with the deck anchors.
  2. Secure the springs to each anchor using the provided tool.
  3. Ensure the cover is taut with no sagging areas where children or pets could get trapped.
  4. For solid covers, ensure the automatic cover pump is in place and working.

Tarp/Water Bag Covers

  1. Spread the cover, leaving 3–4 feet of overlap on all sides.
  2. Place water bags (⅔ full, not completely full — they need room to expand when they freeze) around the perimeter, end to end.
  3. For above-ground pools, inflate and position the air pillow before laying the cover.

Closing Timeline Checklist

Step ☐ Time
Balance chemistry (pH, TA, CH, CYA) ☐ 30 min
Super-chlorinate / shock ☐ 15 min
Add winter algaecide and stain preventer ☐ 10 min
Run pump 24 hours for circulation ☐ —
Brush, vacuum, skim, clean waterline ☐ 1–2 hrs
Clean/backwash filter ☐ 30 min
Lower water level ☐ 1–3 hrs (pump or siphon)
Remove drain plugs from all equipment ☐ 15 min
Blow out all plumbing lines ☐ 45–90 min
Install winterizing plugs and gizzmos ☐ 15 min
Add antifreeze to skimmers and lines ☐ 15 min
Remove and store accessories ☐ 20 min
Install winter cover ☐ 30–60 min
Turn off breakers, shut off gas ☐ 5 min
💰 Cost Summary:
• DIY closing (chemicals + supplies): $50–100
• Professional closing service: $150–350 (includes chemicals and labor)
• First winter cover (one-time): $50–200 (tarp) / $1,500–3,500 (safety cover)
• Cost of NOT closing properly (freeze damage): $500–5,000+

Common Closing Mistakes

Mistake Consequence Prevention
Closing while water is still warm (70°F+) Algae thrives under the cover; awful green mess in spring Wait until water temp consistently stays below 65°F
Skipping the plumbing blowout Cracked pipes, broken fittings, damaged equipment Blow every line until bubbles appear, then plug and add antifreeze
Forgetting equipment drain plugs Pump housing, filter tank, or heater cracks from expanding ice Remove ALL drain plugs; store them in the pump basket
Not shocking before closing Chlorine depletes within weeks; algae takes over under the cover Super-chlorinate to 10+ ppm and add winter algaecide
Using automotive antifreeze Ethylene glycol is toxic to humans, animals, and will contaminate your pool Use ONLY propylene glycol pool antifreeze
Draining the pool completely Hydrostatic pressure can pop the pool out of the ground or crack the shell Only lower to the recommended level for your cover type

Warm-Climate Considerations

If you live in an area where freezing is rare or nonexistent (Florida, Southern California, Arizona, Gulf Coast):

  • You may not need to “close” at all. Many warm-climate pools run year-round with reduced pump runtime (4–6 hours/day in winter).
  • Reduce chlorine demand with lower pump times and a maintained CYA level.
  • Keep an eye on phosphates — falling leaves in autumn spike phosphate levels, which feed algae.
  • If you get occasional freezes, enable freeze protection on your automation system. It runs the pump when air temps drop near 35°F.
  • If you choose to close for the off-season, follow all the chemistry steps above but you can skip the plumbing blowout and antifreeze.

Mid-Winter Checks

Even a properly closed pool benefits from occasional monitoring:

  • Monthly: Check the cover for damage, excessive water accumulation (pump it off), or sagging.
  • After storms: Remove heavy snow loads from the cover to prevent damage. Use a soft broom — not a shovel.
  • Check water level: If visible through or around the cover, ensure it hasn’t dropped significantly (possible leak).
  • Verify cover pump is working (solid covers only) — standing water on a solid cover can cause collapse.

Frequently Asked Questions

Can I close the pool myself, or should I hire a professional?

Most pool owners can close their own pool. The hardest part is blowing out the plumbing lines — if you have a compressor or shop vac and are comfortable with your plumbing layout, you can do it. The first time is the hardest; after that, it’s routine. That said, if you’re unsure about the plumbing or have complex equipment, a professional closing ($150–350) is cheap insurance against freeze damage.

What if I forget to winterize and a freeze is coming?

Emergency measures: (1) Run the pump continuously — moving water resists freezing. (2) Open the bleeder valve on the filter slightly to allow slow dripping, which prevents freezing in the filter. (3) If power might go out, open all drain plugs on equipment to let water drain by gravity. (4) Add antifreeze to skimmers as insurance. Then properly winterize as soon as possible.

Do I need to add chemicals during winter?

Generally no, if you balanced and shocked properly at closing. Some owners add a mid-winter dose of algaecide for long winters (5+ months under the cover), but it’s usually unnecessary with good closing chemistry.

How do I know if my pipes froze?

You often won’t know until spring. Signs: cracked pipes visible at the equipment pad, PVC fittings that are split or pushed apart, a pump housing with a crack, or a filter tank that’s cracked. Water level dropping faster than evaporation accounts for suggests an underground pipe crack. If you find freeze damage, call a pool professional for assessment before starting the system.

Should I leave the breaker on for freeze protection?

If you have an automation system with freeze protection and you experience intermittent freezes before full winterization, yes — leave the breaker on and the freeze protection enabled. Once you’ve done the full closing procedure (blown out lines, drained equipment), turn the breaker off.

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