As the summer months fade and the weather turns cooler, it’s time to think about preparing your swimming pool for the off-season. Closing a pool correctly is essential to protect your investment, maintain water quality, and prevent costly damage during the cold months. Whether you own an in-ground, above-ground, or saltwater pool, the process involves more than just throwing on a cover. In this comprehensive guide, we will walk you through all the steps, tools, and best practices you need to successfully close your swimming pool for winter.
Why Closing Your Pool for Winter Matters
Before diving into the process, it’s important to understand why winterizing your pool is not just a luxury but a necessity. A poorly closed pool can suffer from algae overgrowth, chemical imbalance, and even structural damage. Cold temperatures can cause water to freeze and expand, potentially cracking pipes, pumps, filters, and the pool structure itself.
Moreover, neglecting proper water chemistry before closing can lead to staining, corrosion, and the development of biofilm in your filtration system. By investing a few hours into proper closure, you’re saving yourself potential repair costs, and ensuring a much easier and cleaner startup in the spring.
Timing Your Pool Closure: When to Do It
The ideal time to close your swimming pool varies depending on your local climate and how frequently you use the pool. However, a general rule of thumb is to close your pool when the water temperature consistently drops below 65°F (18°C).
At this point, algae and bacteria growth significantly slows down, making it easier to balance water chemistry for winter storage. Closing too early can lead to algae problems, while waiting too long can risk freeze damage to equipment.
Key Indicators for Pool Closure
- Water temperature below 65°F
- Debris accumulation increases despite regular cleaning
- Average daily temperatures drop below 60°F
- Reduced pool usage due to cold weather
Gathering the Necessary Tools and Supplies
Before starting the closing process, ensure you have all the essential tools and chemicals on hand. The right supplies will help you efficiently and effectively winterize your pool without delays or multiple trips to the pool store.
Essential Supplies for Pool Closure
| Item | Purpose |
|---|---|
| Closing chemical kit (algaecide, winterizing chemical, stain preventer) | Used to balance water and prevent algae and staining |
| Pool cover (solid or mesh) | Prevents debris and water from entering the pool |
| Cover pump | Removes standing water from the pool cover |
| Winter plugs or air plugs | Seal pipes and jets to prevent freezing |
| Basket plugs or test plugs | Used to plug equipment returns in the pool |
| Winterizing test strips or kit | For accurate water testing before closing |
| Foam pipe plugs or shop vac | Used to remove water from lines and protect against freezes |
Step-by-Step Pool Closure Process
The closure process can be broken down into several clear steps, each playing a vital role in proper winterization. Let’s dive into each task in detail.
Step 1: Balance the Water Chemistry
Before shocking and adding winter chemicals, it is critical to balance the water’s pH, total alkalinity, calcium hardness, and stabilizer levels. Imbalanced water can lead to staining, scaling, and metal corrosion over the winter months.
Target Levels for Winter Water Chemistry:
- pH: 7.4–7.6
- Total Alkalinity: 80–120 ppm
- Calcium Hardness: 200–400 ppm for concrete pools; 150–250 ppm for vinyl
- Cyanuric Acid (Stabilizer): 30–50 ppm
To achieve these levels, use your test kit or test strips. Make adjustments gradually with pH increasers or decreasers, alkalinity boosters, or calcium hardness adjusters, and allow enough time for the chemicals to circulate before proceeding.
Step 2: Clean and Skim the Pool
Start by manually cleaning your pool using a skimmer net and vacuum. Remove large debris such as leaves, twigs, and dirt from the surface and the bottom. Then, brush the walls and corners of your pool thoroughly. This ensures that any organic material or contaminants that can promote algae growth are removed before winterizing chemicals are applied.
If you’re using a robotic or manual pool vacuum, ensure the entire bottom is free of sediment. Skipping this step can lead to cloudy water and stubborn stains upon opening your pool next spring.
Step 3: Shock the Pool
Shocking the pool before closing eliminates bacteria and organic contaminants, and ensures that the remaining chlorine can effectively combat any dormant algae spores.
We recommend using a non-chlorine shock for this step if you use a chlorine-based winterizer, to avoid overdosing chlorine levels. If your winterizer uses chlorine, you may use a chlorine shock instead. Perform this at dusk to prevent UV degradation.
Step 4: Add Winterizing Chemicals
The pool is now ready for winterizing treatment. The typical winterizing chemical pack includes a long-lasting algaecide (often copper or quat-based), a stain preventer, and sometimes a clarifier.
These chemicals:
- Inhibit algae growth during dormancy
- Bind metals like iron that can lead to staining
- Clarify the water to reduce cloudiness post-winter
Follow the manufacturer’s instructions for dosage. Do not mix chemicals unless specified. After application, run the pump for 2–4 hours to ensure proper distribution.
Step 5: Lower the Water Level
To protect the pool cover and prevent overflow from rain or snowmelt, begin lowering the water level slightly below the skimmer.
The water should be lowered to just a few inches below the skimmer or return jet, depending on your pool type. For some vinyl pools and above-ground pools, you may not need to lower the water level significantly—always verify this based on manufacturer guidelines.
Step 6: Winterize the Pool Equipment
Don’t neglect your pool equipment when closing for the winter—it’s just as important as the water treatment and cover placement.
Turn Off and Drain the Pump and Filter
First, turn off the pool pump and filter system completely and set the multiport valve (if applicable) to the “closed” position. Then open the pump’s drain plugs and filter valves to let water drain out. This prevents freeze damage from water expanding inside these components.
Blow Out the Plumbing Lines
Using an air compressor or a leaf blower (set to low pressure), blow air through all suction and return lines. This forces the remaining water out of the pipes and into the pool. After blowing out the lines, insert PVC air plugs or foam noodles into each line to keep water from re-entering.
Winterize the Saltwater Chlorinator (if applicable)
If you have a saltwater system, you’ll need to remove the saltwater cell and winterize it by soaking it in a muriatic acid cleaning solution (as per manufacturer instructions). Rinse and store it in a dry, safe place.
Step 7: Install the Pool Cover
Choosing the right cover and properly installing it can make a big difference in how much upkeep your pool needs during winter.
Choosing Between Solid or Mesh Covers
- Solid pool covers are best for areas with heavy rainfall and falling debris. They block sunlight, preventing algae growth and keeping contaminants out.
- Mesh covers allow water to pass through but trap debris. These are ideal for areas with heavy snowmelt or rain that you don’t want to pool on top of the cover.
Use a cover tightener or water bags to secure the edges around the deck and ensure your cover doesn’t flap in the wind or let debris inside.
Adding Water Tubes or Cover Holders
To effectively anchor your cover, place water tubes or bags along the edges. These filled bags act as weights and ensure that the cover doesn’t lift or tear during windy weather.
Using a Leaf Net (Optional)
For extra protection, especially under trees, consider installing a leaf rake-style net over the water before placing the cover. This helps catch leaves and debris without allowing them to settle on the pool surface.
Step 8: Add an Air Pillow (For In-ground Pools)
If you own an in-ground pool in a freezing climate, install a floating air pillow in the center of the pool before closing the cover. This allows for ice expansion upward, reducing the risk of hydrostatic pressure cracking the pool floor or walls.
The pillow should be at least one-third of the pool’s width. Tether it securely so that it doesn’t drift to the edges or touch the walls. In vinyl pools, use a heavy-duty air pillow that can withstand puncture risks.
Closure Checklist for Maximum Safety and Efficiency
To ensure you’ve completed everything needed before closing your pool, follow this straightforward checklist:
| Task | Status |
|---|---|
| Test and balance water chemistry | ✅ / ❌ |
| Skim, brush, and vacuum | ✅ / ❌ |
| Shock the pool with appropriate chemicals | ✅ / ❌ |
| Add winterizing chemicals and run the pump briefly | ✅ / ❌ |
| Lower the water level appropriately | ✅ / ❌ |
| Winterize all equipment (pump, filter, salt cell, etc.) | ✅ / ❌ |
| Install pool cover securely | ✅ / ❌ |
| Place water bags, sandbags, or tighteners | ✅ / ❌ |
| Add an air pillow (if in-ground and freezing climate) | ✅ / ❌ |
Closure of Above-Ground Pools: Special Considerations
Above-ground pools require a slightly different approach than in-ground ones. Given they’re often smaller and simpler in structure, they may not need as many complex winterizing steps, but certain key points remain crucial.
Do You Need to Drain the Pool?
Contrary to popular belief, most above-ground pools do not need to be completely drained. Lower the water approximately four to six inches below the skimmer or return lines. Some manufacturers recommend draining to just below the rails, but always refer to the manufacturer’s instructions.
Winterizing Above-Ground Pool Equipment
Use the same process as for in-ground pools: drain the pump and filter, winterize chemical systems like salt cells, and blow out the lines carefully.
Note: Avoid leaving water in equipment lines when temperatures drop below freezing, as ice expansion can cause cracks or leaks.
Choosing the Right Cover
Since it’s easier to see above-ground pools and they’re often placed in exposed areas, a mesh cover can help reduce standing water on top, while a solid cover protects from leaves and debris. Most above-ground covers come with grommets and can be secured using water tubes or deck anchors.
Dealing with Saltwater Pools
Saltwater pool owners must take a few extra precautions when winterizing their pools. Unlike traditional systems with constant chlorine addition, salt generators produce chlorine on demand and require detailed cleaning to ensure safe off-season storage.
Check Manufacturer Recommendations for Chlorinators
Some modern saltwater chlorinators can remain in place during winter, but most require removal and storage once the pool is properly balanced and chemicals have dissolved.
Rinse and Clean the Salt Cell
Before storing, submerge the salt cell in a solution of water and muriatic acid (or use a commercial salt cell cleaner) to dissolve calcium buildup. Rinse thoroughly and store in a dry, warm area.
Common Mistakes to Avoid When Closing Your Pool
Even the most experienced pool owners can make errors when preparing for winter. Here are some of the most common mistakes to avoid during the closure process:
Inadequate Water Testing Before Closure
Failing to thoroughly test and adjust your pool chemistry before you close can lead to staining, scaling, or metal damage. Don’t skimp on this step—it’s a foundation for proper closure.
Improperly Winterized Equipment
Neglecting to drain water from pumps, filters, and pipes may result in irreversible freeze damage. Every element, including PVC lines, must be winterized or blown dry.
Using Inappropriate Covers
Some pool covers are too thin or unsuitable for climate conditions. Invest in a cover rated for your local weather and ensure it’s properly tied down.
Not Using an Air Pillow in Freezing Climates
Not using an air pillow can result in ice expanding downward instead of upward, potentially cracking plaster finishes or vinyl pool bottoms.
Saving Time on Chemicals
While it’s tempting to save money by limiting pool chemical doses, using subpar or non-specific winterizing chemicals can spell disaster in spring. Always opt for high-quality pool closure kits.
Final Thoughts: Why Proper Closure Pays Off
Closing your pool for the winter isn’t a chore—it’s an investment in your pool’s longevity, appearance, and usability. Following a detailed process helps prevent costly repairs, improves startup efficiency next year, and keeps your pool in top shape for years to come.
Whether you’re using an in-ground or an above-ground pool, a smart and thorough closure plan will ensure your backyard’s focal point is always ready for action when warm weather returns. With proper planning, attention to chemistry, and a quality cover, you can rest easy knowing your pool is protected all through winter.
Now that you’re equipped with the knowledge and checklist on what is needed to close a pool for winter, you’re ready to tackle pool closure with confidence and precision.
Why is it important to winterize my swimming pool?
Winterizing your swimming pool is crucial to protect the structure and equipment from damage caused by freezing temperatures. Water left in the pool lines, filters, or the pool itself can freeze, expand, and lead to cracks in the plumbing, tiles, or even the pool shell. Proper winterization helps maintain water quality and prevents costly repairs, ensuring your pool is in excellent condition when you’re ready to open it again in the spring.
This process also safeguards your investment by prolonging the life of pool components such as pumps, heaters, and filters. Additionally, properly winterized pools are less likely to accumulate algae or suffer chemical imbalances during the off-season. Taking the time to follow each step carefully will make reopening the pool much easier and less time-consuming when warmer weather returns.
When is the best time to close my pool for the winter?
The ideal time to close your pool depends on your geographic location and local climate, but generally, it’s best to do so when the water temperature consistently drops below 65°F (18°C), usually in late fall. Waiting until the swimming season has clearly ended ensures that you won’t have to clean or balance the water again before covering the pool. However, you should close your pool before the first hard freeze to avoid damage from freezing temperatures.
Closing your pool too early can lead to algae growth and water imbalance due to warm spells, while waiting too long increases the risk of cold-weather damage. Pay attention to local weather forecasts and plan to winterize your pool when you expect extended cooler conditions. If you’re unsure, consult with a local pool professional who understands regional climate patterns.
What chemical steps should I take before closing my pool?
Before closing your pool, it’s important to balance the water chemistry to prevent problems over the winter months. Begin by testing the pH, alkalinity, calcium hardness, and chlorine levels, adjusting them to recommended winter levels. Maintaining a pH between 7.2 and 7.6, alkalinity between 80-120 ppm, and calcium hardness between 200-400 ppm will reduce the risk of corrosion and staining.
Once the water is balanced, shock the pool with a chlorine-based shock to eliminate any bacteria or algae. After shocking, add a winter algaecide to keep algae growth at bay. Letting the water circulate for a few hours after chemical additions ensures even distribution. These steps will keep your water clear and protected throughout the colder months.
Should I drain my pool completely for the winter?
In most cases, you should not drain your in-ground pool completely for winter, as this can lead to structural damage from ground water pressure or pool shifting. Instead, lower the water level to just below the skimmer and return jets to protect plumbing lines. For above-ground pools, you may be instructed to drain completely or partially, depending on the type of cover being used. Always follow manufacturer recommendations for your particular pool type.
Draining too much can also cause damage, such as collapsing of vinyl liners or cracking of fiberglass and concrete surfaces. Leaving the proper water level will also make it easier to clean and refill the pool in the spring. Never leave standing water without proper chemical treatment, as this can become a breeding ground for algae or insects. For optimal results, use a winter cover to keep debris out and maintain water levels.
What kind of cover should I use for winterizing my pool?
When choosing a cover for winter pool closure, a durable, high-quality solid or mesh safety cover is the best option. Solid covers block debris and sunlight, reducing algae growth and keeping the water cleaner through the winter. Mesh covers, on the other hand, allow water to drain through, which can be useful for areas with heavy rain or snow melt, but they do not stop fine debris entirely and may require more spring cleaning.
Covers should be securely fastened to prevent displacement from wind or heavy snowfall. Use water bags or cover clips to anchor your cover tightly to the pool deck. It’s also important that your chosen cover fits your pool properly to avoid sagging, tearing, or leaving gaps for leaves and debris to enter. Spending the extra money on a quality winter cover can significantly reduce maintenance work when reopening the pool.
How do I winterize my pool’s plumbing and filtration system?
To properly winterize your pool’s plumbing, begin by blowing out the lines using an air compressor to remove all remaining water. This prevents freezing and cracking during cold weather. Add a non-toxic pool antifreeze into the lines after blowing them out for extra protection, particularly in areas that experience prolonged freezing temperatures. Ensure that all valves are properly set to prevent water from returning to the system.
Next, drain the pool pump, filter, and heater completely. Leave the filter’s multiport valve in the “open” position and remove the drain plugs to allow any residual water to escape. If your equipment does not recommend antifreeze, store parts indoors in a frost-free location. Covering your equipment with a tarp will protect it from the elements and keep it dry and safe throughout the winter season.
What are the key maintenance tasks to ensure a smooth re-opening in spring?
Even during winter, minimal maintenance can greatly ease the pool opening process. Periodically check that the cover is secure and that water levels under the cover are within an appropriate range—not too high or too low. Remove any heavy debris accumulation on the cover so it doesn’t become a strain on the material or pool structure. Occasionally check skimmer baskets and pool surroundings for any potential issues like shifting covers or animal activity.
Before opening the pool in spring, remove the cover, clean it, and store it in a dry place to preserve its lifespan. Begin refilling the pool if the water level has dropped significantly, then start the filtration system once everything is reconnected. Test water chemistry and begin balance and sanitization as needed. Cleaning the pool thoroughly, brushing walls, and vacuuming debris will help restore clarity and cleanliness after the off-season.