Closing your pool for winter takes a little planning, but skipping the wrong step can leave you with cracked pipes or a mess to clean up come spring. Knowing how to winterize a pool protects your equipment and makes reopening day much easier.
At Benchmark Pool Supply, we help pool owners choose the right pool chemicals and equipment for the job. Here's how to prepare your water, protect your plumbing, and close your pool for the winter without missing the details that matter.
When Should You Close Your Inground Pool for Winter?
The best time to close your pool is when the water consistently reaches around 60°F or below, but before freezing weather arrives. Cooler water slows algae growth under the cover, while waiting too long puts your pipes and equipment at risk. Water left inside can freeze, expand, and crack fittings or damage your pump and filter.
Closing season varies depending on where you live:
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Northeast and Midwest: Typically September through October.
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Mid-Atlantic: Often October through November.
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South and Southwest: Some pools stay open year-round, depending on local temperatures.
These timelines are a starting point. Monitor water temperature and the local forecast to allow enough time to close before the first hard freeze.
Do You Need to Close a Pool in Warm Climates?
In warmer areas like much of California, you may not need to close your pool completely. A partial pool closing lets you keep the pool operating with adjusted winter maintenance. You'll still need to balance the water and protect equipment when freezing temperatures are in the forecast.
What Chemicals Do You Need to Winterize a Pool?
Before stocking up on closing chemicals, test your pool water. Your results will help you choose the right pool shock and winterizing chemicals without buying treatments you don't need.
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Pool Shock: Raises chlorine levels to address contaminants before closing. Follow the product label and your water test results to determine the proper dose.
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Winter Algaecide: Helps control algae during the off-season. Polyquat-based products are popular, but dosage depends on pool volume and product concentration.
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pH Adjusters: Keep pH around 7.2–7.8. If levels are too high, use muriatic acid to bring them back into range.
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Alkalinity Adjusters: Keep total alkalinity around 80–120 ppm to help stabilize pH.
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Calcium Hardness Adjusters: Maintain the appropriate calcium level for your pool's surface and water balance to help prevent scaling or surface damage.
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Stain and Scale Preventers: Consider these when water conditions or metal content raise concerns about staining and deposits.
How to Balance Chemistry Before Closing
Test your water five to seven days before closing, then adjust alkalinity, pH, and calcium hardness as needed. Once balanced, shock the pool according to the product directions and let chlorine drop to the level recommended for your algaecide before adding it. Never mix concentrated pool chemicals.
What's in a Winterization Chemical Kit?
A pool winterization chemical kit makes it easier to gather essentials like shock and algaecide. Make sure the kit matches your pool's size and water chemistry before buying.
Special Considerations for Salt Water Pools
Saltwater pools follow the same basic winterization process, but the chlorine generator needs extra attention. As water temperatures drop, your system may stop producing chlorine, so check your levels before closing. Shut off the generator and clean, remove, or protect the salt cell according to the manufacturer's instructions.
Step-by-Step: How to Winterize an Inground Pool
Step 1 — Clean the Pool Thoroughly
Remove leaves and debris, then scrub the walls and steps with a pool brush. Use a pool vacuum hose to clean the floor before emptying the skimmer and pump baskets. This keeps leftover debris from encouraging algae growth under the cover.
Step 2 — Balance Chemistry and Shock the Pool
With the pool clean, follow the chemical treatment order outlined above. Keep the pump running long enough to circulate each treatment, and check your chlorine level before adding winter algaecide.
Step 3 — Lower the Water Level
After circulating the treatments, use a submersible pump or your filter's waste setting (if available) to lower the water level. Your pool and cover determine how far to drain, so check their requirements first. Never empty an in-ground pool completely, as groundwater pressure can damage the shell or liner.
Step 4 — Blow Out and Plug the Plumbing Lines
With the water at the proper level, use a pool winterization blower to clear the skimmer, return, and other applicable plumbing lines. Seal them with the correct winterizing plugs, protect the skimmer with a compatible device, and use pool-grade antifreeze only where recommended. Keep air pressure within equipment specifications to avoid damaging fittings.
Benchmark Tip: Not sure which lines need clearing or how to seal them? Have a pool professional handle the blowout before freezing temperatures arrive.
Step 5 — Remove, Drain, and Store Equipment
Next, drain your pump, heater, and filter according to their manufacturer's instructions. Cartridge, sand, and DE filters each have different closing procedures. Proper pool filter care helps protect your equipment from avoidable damage.
Step 6 — Install the Winter Cover
Finish by installing a properly fitted winter cover. Secure the straps or water bags as directed, and avoid bricks or concrete blocks that could damage the pool. If you need a safety barrier, choose a cover specifically rated for that purpose. For solid covers that collect rainwater, use a compatible cover pump to prevent excess water from building up.
Winterization Mistakes That Cause the Most Damage
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Closing Too Early: Algae can keep growing under the cover when the water is still warm, leaving you with a tougher cleanup in spring.
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Leaving Water in the Lines: Even a small amount of trapped water can freeze and damage fittings. Double-check that each line has been cleared and sealed.
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Adding Chemicals Too Close Together: High chlorine levels can interfere with some algaecides. Follow product instructions and allow enough time between treatments.
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Using the Wrong Antifreeze: Automotive antifreeze contains chemicals that don't belong in pool plumbing. Use only antifreeze specifically labeled for pool winterization.
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Forgetting About the Cover: Heavy debris or standing water can put extra strain on your cover. Inspect it after storms and clear buildup before it becomes a problem.
Avoiding these mistakes starts with the right supplies and advice. Benchmark Pool Supply makes learning how to winterize your pool easy with a comprehensive selection of products and resources. Stop by or call our team today to close your pool with confidence and make spring reopening easier.
FAQ — Winterizing an Inground Pool
What Chemicals Do You Put in a Pool for Winter?
You'll typically need pool shock and winter algaecide, along with chemicals to balance your pH and alkalinity. Depending on your water test results, you may also need a calcium hardness adjuster or stain preventer. Test your water first, so you add only what's needed.
How Much Does It Cost to Close a Pool for Winter?
DIY pool closing supplies may cost around $150-$300, while professional winterization can range from $200-$500 or more. Your final cost depends on your pool size, equipment, and local service rates. These are general estimates, not Benchmark Pool Supply prices.
How Far Down Should I Drain My Pool for Winter?
It depends on your pool and winter cover. Some covers require water below the skimmer, while others need a higher water level for support. Check your cover manufacturer's instructions before draining, and never empty an in-ground pool completely.
Can You Winterize a Pool Without Covering It?
Yes, especially in warmer climates where freezing isn't a concern. However, leaving your pool uncovered means dealing with more debris and upkeep. In colder regions, a winter cover helps protect the closed pool, but you'll still need to winterize the plumbing and equipment.
How Do You Winterize an Above-Ground Pool Differently?
Above-ground pools follow a similar closing process, but you'll typically need to disconnect hoses, plug openings, and secure the winter cover with a cable and winch. The exact steps depend on your pool setup, so check the manufacturer's instructions before lowering the water or disconnecting equipment.
