When the summer swimming season ends, many pool owners face the question: what’s the proper way to winterize a pool? Winterization is a critical process that ensures your pool remains protected during the cold season, preventing costly repairs and extending the life of your investment. If done correctly, winterizing your pool safeguards equipment, prevents algae growth, and keeps water chemistry balanced until you’re ready to swim again.
This comprehensive guide walks you through every essential step of winterizing your pool, whether it’s above-ground, in-ground, or an above-ground with a sand or salt system. We’ll help you understand best practices, necessary tools, and what to avoid in order to maintain your pool’s condition year-round.
Why Winterizing Your Pool Matters
Properly winterizing your pool is more than just covering it up—it’s about protecting your pool structure, equipment, and water from frost, debris, and stagnant conditions that can lead to expensive problems. During winter, water can freeze and expand, causing damage to pipes, pumps, and filters. An improperly winterized pool may also promote algae growth or become cloudy and unbalanced, making spring reopening more difficult and chemical-heavy.
Here’s what winterizing protects against:
- Freeze damage to plumbing, pump, and filter
- Algae infestation and water discoloration
- Cracks in pool surface or tiles
- Corrosion of metal parts
If you live in a climate where temperatures drop below freezing, winterizing is non-negotiable.
Before You Start: Gathering the Right Tools and Supplies
Proper pool winterization requires some planning and the right materials. Below is a list of essential tools and chemicals:
Essential Equipment and Supplies:
- Winter pool cover (solid or mesh)
- Pool cover clips or water bags
- Anti-algae chemicals (winterizing algaecide)
- Winterizing chemical kit (includes shock and enzymes)
- Pool brush and vacuum
- Skimmer and hose plugs (freeze plugs)
- Drain plugs for equipment
- Air compressor or shop vacuum (for blowing out lines)
- Bucket-style leaf net (if you have trees nearby)
- Winter cover pump
Choosing a durable winter pool cover is crucial. A solid cover blocks sunlight and prevents debris from entering. Mesh covers allow water through but still keep large debris out. Make sure the cover fits your pool tightly and is UV-resistant.
Step-by-Step Guide to Winterize Your Pool
Here’s a step-by-step procedure to winterize your pool the right way. This process may vary slightly depending on the type of pool (above-ground vs. in-ground) and filter type (sand, cartridge, or DE), but we’ll cover all bases.
Step 1: Prepare Water Chemistry
Before shutting down your pool, it’s essential to balance the water properly. Start this phase 5–7 days before winterizing to ensure all chemicals stabilize.
Test Water Chemistry:
- Ph Level: Around 7.2–7.6
- Alkalinity: 80–120 ppm
- Calcium Hardness: 150–400 ppm (200–250 ppm for vinyl pools)
- Chlorine: 0–0.3 ppm before shocking
Once balanced, shock the pool with a winter-strength shock, often calcium hypochlorite. This removes any present contaminants, ensuring a cleaner startup in the spring.
Step 2: Clean the Pool Thoroughly
A clean pool ensures fewer issues when reopening. Follow these sub-steps:
Read more: How Often Should You Clean Your Pool?
Cleaning Steps:
- Remove all surface debris with a skimmer net
- Brush the walls, tile line, and floor
- Vacuum manually or use an automatic pool cleaner
- Clean filter and pump baskets
- Backwash filter (cartridge or DE)
Use a pool tile cleaner to scrub the waterline where oils and residue accumulate.
Step 3: Lower Water Level (Depending on Pool Type)
Reducing the water level protects against freeze expansion. The right level depends on the type of pool:
Water Level Guidelines:
| Pool Type | Proper Winter Water Level |
|---|---|
| In-Ground (Vinyl/Concrete) | 4–6 inches below the skimmer opening |
| In-Ground Fiberglass | Below the tile line or as per manufacturer instructions |
| Above-Ground | 3–4 inches below the skimmer or as directed by manufacturer |
Use a submersible pump or your pool’s drain setting to lower the water level safely.
Step 4: Drain Water from Pumps, Filters, and Pipes
This step prevents water-filled pipes from freezing and cracking.
Pump Draining Procedure:
- Turn off power at the circuit breaker
- Unscrew any drain plugs or open drain valves on the pump
- Leave open during storage to ensure water drains fully
Filter Winterizing:
- Drain DE and cartridge filters entirely by opening drain valves
- For sand filters: use winterizing mode or install winter plugs
Bleed Pressure from Valves:**:
To help with complete drainage, open air relief valves after backwashing or rinsing the filter. Also, do not leave filter valves in the backwash position.
Step 5: Protect Plumbing Lines by Blowing Out or Using Antifreeze
There are two effective ways to protect pipes: blowing air through the lines or using non-toxic antifreeze.
Blow Out Method:
Using an air compressor or a leaf blower is a common DIY method. The process involves blowing out water from all lines and fitting:
- Attach the air hose to the return line
- Blow air through until all water is expelled
- Repeat for skimmer and main drain lines
Antifreeze Method:
Alternatively, pour winterizing pool antifreeze into each plumbing line. Ensure it is non-toxic and compatible with pool systems.
Never mix air blowing and antifreeze methods.
Step 6: Install Skimmer and Return Plugs
After draining lines, install threaded freeze plugs in the skimmer and return lines. These vinyl or plastic plugs block water from re-entering the lines and contain air during freeze expansion, protecting the plumbing.
Use expanding foam to insulate the skimmer basket before you plug it. This can help prevent cracks from temperature changes.
Step 7: Chemically Treat the Water
Before covering, maintain winter water quality with the right chemicals:
Chemical Application Steps:
- Add winter algaecide (preferably a copper-based one)
- Add an enzyme-based winter chemical to break down organics
These chemicals help curb algae growth and reduce organic buildup during pool downtime.
Step 8: Cover the Pool Securely
The final step is covering your pool effectively. A poorly secured cover can allow debris in, create water pockets, and damage the cover itself.
How to Secure a Pool Cover:
- Stretch the cover over the pool tightly
- Use cover clips or water bags around the edge
- Ensure there is a slight slant or slope for water drainage
- Place a pool cover pump on the inside to remove rainwater
For sand or saltwater pools, consider wrapping the salt cell to protect metal components from corrosion due to stagnant water.
Special Considerations for Different Pool Types
Different types of pools—such as saltwater, sand-filtered, above-ground, and gunite/in-ground—require slight modifications in winterizing.
Saltwater Pools
Saltwater pool systems need extra care. Because salt can corrode metal parts, draining the salt cell and pump is especially important.
Step-by-Step Saltwater Pool Winterization:
- Drain salt chlorine generator unit
- Remove and store salt cell for inspection and cleaning
- Verify all electronics are dry and off
Above-Ground Pools
For above-ground pools, you can either partially drain and winterize or remove the water completely (depending on construction and local climate). Most above-ground pools are drained lower than in-ground pools to avoid damage to the metal walls.
Winterization Tips:
- Use a dome cover or solid cover with support bars
- Install a cover pump to avoid excess weight
- Cover should be tight but not stretching
Gunite or Concrete In-Ground Pools
Gunite pools are durable but still susceptible to freezing. Balance water chemistry and lower water level properly before covering. Tile lines are especially prone to staining when left idle.
Remove ladders and diving boards to avoid corrosion and structural pressure from ice.
Winter Maintenance While the Pool is Covered
Winterizing doesn’t end once the cover is on. Proper winter maintenance keeps issues at bay and reduces workload come spring.
Regular Inspections
Check your pool weekly (or monthly in moderate climates) for:
– Cover damage or looseness
– Pool cover pump operation
– Leaf buildup or heavy snow
Adding Winter Algaecide or Bactericide Mid-Season
If water has not been treated properly or you notice discoloration, add additional algaecide through slits in the cover. It’s best done during mild spells without snowfall.
Draining Snowmelt and Rainwater
Standing water on the pool cover causes stretching and strain. Use the cover pump regularly, and consider manually redistributing large water pockets to prevent damage.
What NOT to Do When Winterizing Your Pool
A little misinformation can lead to mistakes that undo good winterization efforts. Here are some common winterizing missteps to avoid.
Don’t Leave the Water Untreated
Even if the pool is “just going to sit,” it’s never a good idea to avoid winterizing chemicals. Untreated water can develop algae, turn green, and cause metal corrosion.
Don’t Use a Regular Tarp Instead of a Pool Cover
Tarps won’t withstand the weight of snow or debris and are not UV-resistant. They can also tear or puncture more easily, letting in water and dirt.
Avoid Using Automotive or RV Antifreeze
Only use winterizing pool antifreeze, which is safe for your system. Automotive antifreeze contains ethylene glycol, which is toxic and can damage pool surfaces.
Conclusion: Winterizing Your Pool Helps You Start Clean in Spring
Taking the proper way to winterize a pool involves more than covering it and calling it a day—it requires a thorough balance of water chemistry, drainage, system shutdown, and chemical treatment. While it may seem like a long process, especially your first time, each step is essential for spring success and long-term maintenance savings.
Investing time in winterizing now will mean less hassle, fewer repairs, and clearer water down the road when the snow melts and warm weather returns. Whether you own a saltwater pool, in-ground concrete pool, or a backyard above-ground, following this guide will ensure your pool structure and equipment are protected throughout the cold months.
So, as the cold season inches closer, take proactive steps to prepare your pool—it’s the best way to prolong its lifespan and make pool opening in spring much smoother.
Why is it important to winterize a pool?
Winterizing a pool is essential to protect it from damage caused by freezing temperatures, debris accumulation, and chemical imbalances during the off-season. Failing to prepare your pool for winter can result in costly repairs, such as cracked tiles, damaged pipes, or deterioration of the pool surface. Proper winterization helps maintain water quality and reduces the workload when reopening the pool in the spring.
Additionally, winterizing prevents water from freezing and expanding inside the plumbing lines and equipment, which can cause significant structural damage. By taking the time to properly close your pool for the winter, you ensure its longevity and functionality, saving time, money, and effort in the long run. For these reasons, winterization should be a priority for any pool owner living in a climate with cold winters.
When should I start winterizing my pool?
The ideal time to begin winterizing your pool is when the water temperature consistently drops below 65°F (18°C), typically in late summer or early fall before freezing temperatures arrive. Starting the process early allows you to complete each step thoroughly and ensures the pool is closed before winter weather sets in. If you wait too long, you risk algae growth and equipment damage due to colder temperatures.
Timing can vary depending on your geographic location, so it’s important to monitor local weather forecasts and plan accordingly. Once winterization begins, it typically takes a few days to complete, especially when factoring in water testing and chemical balancing. Getting started at the right time will lead to a smoother and more effective pool closure.
Do I need to drain my pool completely during winterization?
No, you do not need to drain your pool completely when winterizing it. In fact, completely draining a pool can be dangerous and cause structural damage, especially in in-ground pools, where hydrostatic pressure from groundwater can lift or crack the pool shell. It’s generally recommended to lower the water level slightly below the skimmer and return jets to prevent freezing water from damaging these components.
For above-ground pools, draining too much water can also lead to instability and damage from wind or heavy snow. The correct water level depends on the pool type and the cover being used. Always consult the manufacturer’s guidelines for your specific pool and cover system to ensure you’re draining the proper amount while maintaining structural integrity.
What chemicals should I use before closing the pool for winter?
Before closing your pool for the winter, it’s critical to balance the water chemistry to prevent algae growth, bacterial buildup, and staining during the off-season. Start by testing and adjusting pH (ideally between 7.2 and 7.6), total alkalinity (80–120 ppm), calcium hardness (200–400 ppm), and sanitizer levels. Once balanced, use a winterizing kit that typically includes algaecide, a closing chemical pack, and a chlorine shock to eliminate any remaining microorganisms.
Additionally, consider using a phosphate remover and stain inhibitor if your area experiences high levels of debris or mineral-rich water. These extra treatments help preserve the water clarity and prevent staining on pool surfaces. Adding the right chemicals ensures your pool water remains stable throughout winter and makes the spring opening process significantly easier and more manageable.
How do I prepare my pool equipment for winter?
Winterizing pool equipment begins by cleaning or replacing filters and ensuring all components are dry to prevent mold and corrosion. After closing the pool, you should remove the ladder, diving board, and any pool toys, then thoroughly clean them before storing indoors. All equipment, such as pumps, heaters, and chlorinators, should be winterized by draining water from their interiors and applying non-toxic antifreeze where needed.
Next, blow out the lines using an air compressor or a wet vacuum to remove any residual water. Once the lines are clear, install winterizing plugs to seal them. Turn off the circuit breaker to the pump and heater to avoid accidental operation. Finally, cover all equipment to protect it from moisture, ice, and debris. Proper preparation protects your investment and helps everything function smoothly when you reopen the pool.
Do I need a pool cover, and what kind is best?
Yes, using a pool cover is one of the most important steps in winterizing your pool. A good pool cover protects the water from debris, prevents evaporation, and enhances safety by reducing the risk of accidents during the off-season. There are three main types of winter pool covers: mesh covers, solid covers, and automatic covers. Mesh covers allow water to drain through while blocking leaves and larger debris, which is ideal for areas with heavy rainfall or snowmelt.
Solid covers, which are usually blue or opaque, prevent debris and sunlight from entering the pool, reducing the likelihood of algae growth underneath the cover. They require the use of a water bag or cover pump to manage standing water. Automatic covers are motorized systems that provide convenience and superior protection but come at a higher cost. Selecting the right cover depends on your budget, climate, and how much maintenance you’re willing to perform during the winter months.
Can I winterize a saltwater pool the same way as a chlorine pool?
While the basic principles of winterization are similar for both saltwater and chlorine pools, there are specific considerations for saltwater pools. First, test and balance the water, especially chlorine levels, which should be reduced before adding winter chemicals. Saltwater pools still require algaecide and sanitizer before closing to prevent algae growth. However, it’s also important to flush out the salt cell and inspect it for scale buildup, which can impair its performance in the spring.
Additionally, pool owners should turn off and winterize the salt chlorine generator to prevent damage from freezing temperatures. Draining equipment and water lines remains a priority, and ensuring the pool cover is secure is just as critical for saltwater pools. Taking extra care with the salt chlorine generator and cleaning all surfaces exposed to saltwater will help prevent corrosion and extend the life of your equipment. Always consult your system’s manual and manufacturer recommendations for winterizing a saltwater pool.