Maintaining a swimming pool during the off-season can be a confusing task for many homeowners. One of the most common questions pool owners ask as the temperature drops is: Should you leave water in a pool over winter? Whether you’re a seasoned pool owner or new to the world of pool care, the decision to keep or drain your pool for the winter is critical for its longevity and performance.
In this comprehensive guide, we’ll explore the advantages and disadvantages of leaving water in your pool during the winter months. You’ll learn what factors influence this decision, the types of pools affected, and the practical steps needed to properly winterize your pool. By the end, you’ll be equipped to make an informed decision based on your specific situation and climate.
Understanding Winter Pool Maintenance
Before diving into the “to leave or to drain” debate, it’s important to understand what winter pool maintenance entails. When the swimming season ends, pool owners must prepare their pools for months of inactivity. This preparation usually includes chemical balancing, cleaning, and either draining the pool or winterizing it by leaving a certain amount of water in the structure.
Winter pool maintenance prevents damage from freezing temperatures, algae growth, and potential structural issues. The correct approach depends heavily on your pool type, climate, and how well your pool can be sealed and insulated.
The Climate Factor: Why It Matters
The most critical element in deciding whether to leave water in your pool over winter is the climate in your region. In areas where temperatures routinely drop below freezing, water in the pool can freeze and expand, causing damage to the pool’s plumbing, pump, and even the shell itself.
Freezing Temperatures and Pool Damage
When water freezes, it expands. If this happens inside your pool’s pipes, filters, or skimmers, it can lead to cracks and bursts. Pool tiles and coping can also be affected by the pressure caused by ice expansion. These issues can become expensive to repair if not addressed properly before winter begins.
However, even in freezing climates, fully draining a pool can also invite trouble. Without water to stabilize the structure, the pool may float out of the ground due to rising groundwater pressure, particularly in areas with a high water table.
Warm Climate Considerations
In regions where freezing is not a concern, draining your pool over the winter is generally unnecessary. In fact, keeping your pool full can protect the surface from drying out, cracking, or warping. In places like Southern California, Arizona, or Florida, many pools remain operational year-round, while others are maintained with regular cleanings and minimal chemical adjustments during the colder months.
Pool Types That Impact the Decision
Not all pools are designed the same, so it’s important to consider the construction type when deciding whether to leave water in your pool over winter.
Inground Pools
Inground pools are typically built to last through seasonal changes. Most are made of materials like concrete (gunite), fiberglass, or vinyl. Each type requires a slightly different approach:
- Concrete (gunite or plastered) pools: These pools generally need water to keep the surface from drying out and cracking. Proper winterizing is crucial to avoid freeze damage.
- Fiberglass pools: Fiberglass is more resistant to freeze damage, but proper water balance is still important during winter to prevent staining and algae buildup.
- Vinyl-lined pools: These pools are vulnerable to damage from frozen water and should typically have the water level lowered carefully to protect the liner, especially in freezing climates.
Above Ground and Soft-Sided Pools
Above-ground pools and soft-sided pools (often used seasonally) can typically be drained and stored with relative ease. These pools are not usually meant to withstand long periods of freezing temperatures and are designed for disassembly or complete draining during winter.
Pros and Cons of Leaving Water in a Pool Over Winter
Before making your decision, it’s essential to understand the benefits and drawbacks of leaving water in your pool through the winter.
Benefits of Leaving Water in the Pool
- Protection Against Structural Damage: Water pressure helps stabilize the pool structure and prevents floating or shifting due to groundwater pressure.
- Maintenance of Pool Surfaces: Plaster or concrete surfaces can remain moist, preventing cracks due to drying out.
- Easier Spring Opening: If the water remains in the pool, the process of reopening it in the spring is less labor-intensive and less costly.
- Prevention of Airflow and Debris Problems: An empty pool can become a magnet for leaves, dirt, and moisture, leading to mold and mildew issues.
Drawbacks of Leaving Water in the Pool
- Need for Winterization: Leaving water in the pool requires proper chemical balancing and equipment preparation to prevent freezing and algae growth.
- Risk of Freezing Damage: In colder climates, improper winterization can lead to plumbing damage, liner tears, and filter damage due to ice expansion.
- Algae Growth Potential: Even with chemicals, stagnant water can become a breeding ground for algae and bacteria.
- Cost of Winterization Supplies: Chemicals, covers, winterizing kits, and potential professional services can add up annually.
Steps to Properly Winterize Your Pool
If you decide to leave water in your pool over winter, proper winterization is vital. Here’s a step-by-step breakdown of how to prepare your pool for the off-season:
1. Clean the Pool Thoroughly
Start by removing all debris, scrubbing tiles, and vacuuming the pool floor. This minimizes the chance of algae or stains forming during dormancy.
2. Balance the Water Chemistry
Test the pH, alkalinity, hardness, and chlorine levels. The ideal pH level should be between 7.2 and 7.6, with total alkalinity at 80–120 ppm and calcium hardness around 200–400 ppm. Balanced water helps protect against corrosion and plaster damage.
3. Add Winterizing Chemicals
Use a winterizing algaecide and shock treatment to neutralize any remaining contaminants. This step helps keep the water clear and prevents algae blooms when the pool remains covered.
4. Lower the Water Level
For in-ground pools with a solid cover, lower the water level to below the skimmer and return jets. In freezing climates, this minimizes pressure on the plumbing when ice forms.
5. Drain and Winterize the Equipment
Shut off the pump and filter system, and remove all water from the pipes, filter, and pump using air compressors or manual draining. Add pool antifreeze to the lines to prevent freezing.
6. Install a Winter Cover
Use a strong, secure winter cover (typically solid or mesh safety covers). Anchor it properly to prevent loosening, which helps prevent leaves, twigs, and snow runoff from entering the pool.
7. Double-Check and Maintain
Even in the winter, periodic checks are wise. If you notice a significant water level drop or cover displacement, address it promptly to avoid long-term issues.
When It Makes Sense to Drain Your Pool
Although most pools are best left with water in them, there are certain situations when draining makes sense:
Extensive Repairs Needed
If your pool is due for major repairs or renovations, such as replacing the liner, resurfacing the walls, or repairing cracks, it’s best to drain it before starting the project.
Unprotected Pool Location
If your pool is in an area where it can be easily damaged by falling branches, snow buildup, or wildlife, emptying the pool and using a protective cover or dome can make sense.
Certain Above Ground Structures
Some above-ground pool models are designed for seasonal disassembly. If your pool falls into this category, follow the manufacturer’s recommendations for winter storage and draining.
The Myth of Total Draining in Cold Climates
A common misconception is that completely draining a pool protects it from freeze damage. In reality, this often causes more harm than good. A completely empty concrete or fiberglass pool may suffer from structural damage due to unbalanced internal and external pressure from groundwater.
In contrast, partially drained pools with covers are more common in freezing zones. Some pool owners only drain enough water to lower the level below critical equipment points to reduce the ice-related pressure on pipes.
Cheap Covers vs. Proper Winter Covers
Another critical factor in the decision to leave water in your winter pool is the type of cover used. Cheap plastic or mesh covers may allow water, dirt, and animals into your pool, undermining all the effort you put into balancing the chemistry and winterizing the equipment.
A proper safety cover usually consists of reinforced mesh or solid vinyl material. A solid winter cover provides better debris control, while a mesh winter cover allows water to pass through but still holds leaves and debris on the surface.
Some high-end pool owners opt for automatic pool covers or winter dome enclosures, which offer superior protection, especially in harsh climates.
Cost Considerations
The cost of proper winterization and cover installation should be weighed against potential drain-and-fill expenses. Draining a pool requires:
- Disposal fees (if needed due to municipal regulations)
- Refilling costs (including water use fees in some regions)
- Additional chemicals for balancing
In many areas, refilling a pool can cost hundreds of dollars, particularly in drought-affected zones with water restrictions. Therefore, leaving the water in your pool — with proper chemical treatment and a secure cover — is often more economical and environmentally responsible.
Regional Guidelines and Local Expertise
For the most accurate advice, consult with your local pool maintenance professional. They understand the unique weather patterns and soil conditions that affect pools in your area. In some regions, local home improvement stores or municipal water departments also offer winterization guides tailored to your climate.
What Happens if You Forget to Winterize?
Failure to properly winterize can lead to expensive problems. Common issues include:
- Cracked pipes
- Frozen and damaged filtration systems
- Algae overgrowth and staining
- Broken pool covers and excess debris accumulation
In the worst-case scenarios, pool owners may need to invest in full equipment replacement or even professional remediation services.
Tools and Products You’ll Need for Winterization
Here’s a basic list of tools and products to winterize your pool:
| Item | Purpose |
|---|---|
| Pool test kit | To balance water chemistry |
| Winterizing chemicals | To prevent algae during dormancy |
| Pool cover pump | To remove standing water on the cover |
| Winter cover | To protect against debris and evaporation |
| Air compressor | Draining pipes and equipment |
| Winter plugs or skimmer guards | Prevent freeze damage in lines |
Key Takeaways
Do You Leave Water in a Pool Over Winter?
In most cases, the answer is yes, especially for in-ground pools made of concrete, fiberglass, or vinyl. Draining is generally only necessary for short-term repairs or certain portable pool types in non-freezing climates.
Proper Winterization is Critical
Leaving water in the pool is only advisable if you’ve taken the time to balance chemicals, winterize equipment, install a quality cover, and reduce the water level correctly.
Climate Determines Your Strategy
Freezing temperatures affect your pool’s water differently than mild winters. In cold zones, lowering the water level and winterizing equipment is essential, while in warm regions, minimal maintenance during the off-season is sufficient.
Cost and Environmental Responsibility Matter
Draining and refilling can be expensive and wasteful. Leaving water in the pool — when properly winterized — helps conserve resources and lowers long-term maintenance costs.
Final Thoughts
Ultimately, the decision to leave water in your pool over winter must be based on a combination of local climate conditions, your pool’s design, and your willingness to invest in the correct winterization steps. With the right planning, leaving water in your pool can be the more practical, cost-effective, and structurally sound decision — especially for in-ground installations.
If you’re still unsure whether to keep your pool full this winter, consider scheduling a consultation with a professional pool maintenance company. They can help you evaluate local risk factors and recommend the best approach for your specific situation.
By making an informed choice and following proper winterization steps, you’ll be able to enjoy your pool sooner and in better condition when warm weather returns.
Should you leave water in a pool over winter?
Whether you should leave water in your pool over winter depends on several factors including your climate, the type of pool you have, and how well it is maintained. In milder winter climates, keeping the pool full can be manageable with regular maintenance and the use of a quality pool cover. However, in areas with freezing temperatures, it may be necessary to partially or completely drain the pool to prevent ice damage from expansion, particularly for above-ground pools.
For in-ground pools, it’s usually recommended to keep the water at a lower level but not empty. Emptying the pool completely can cause structural damage due to ground water pressure pushing the pool upward. Proper winterization, including balancing the water chemistry and adding winterizing chemicals, is essential to avoid algae growth and protect the pool’s surfaces and equipment during dormancy.
What are the risks of leaving water in a pool over winter?
Leaving water in a pool over winter without proper preparation can lead to several problems, including algae growth, staining, and corrosion of metal components. If the water isn’t chemically balanced and protected with winterizing chemicals, it can become a breeding ground for bacteria and debris buildup under the pool cover. Additionally, fluctuating temperatures and precipitation can cause the water level to change, putting extra stress on the pool structure.
In freezing climates, water left in a pool can freeze and expand, potentially cracking the pool’s tiles, plaster, or even the main structure itself. Ice can also damage pool equipment like skimmers and pipes if water isn’t properly drained and winterized. Without consistent circulation, stagnant water can cause long-term issues that are expensive and time-consuming to repair once spring arrives.
Is it better to drain a pool completely for winter?
Draining a pool completely for winter is generally not recommended, especially for in-ground pools. The empty shell is vulnerable to shifting from ground water pressure or damage from freezing weather. Without water counterbalance, the pool may experience structural issues such as lifting or cracking. However, for above-ground pools, complete draining might be necessary to prevent damage from ice and heavy rain, depending on the model and location.
Instead of full draining, partial draining is often advised for in-ground pools. The water level is lowered to below the skimmer and return jets to protect plumbing and equipment from freezing. This approach maintains enough water to stabilize the structure, while reducing the risk of winter damage. It’s essential to use proper covers and winterizing techniques to protect the exposed surfaces and prevent debris from entering the empty sections of the pool.
How do you properly winterize a pool with water in it?
Winterizing a pool with water in it involves several key steps to ensure the water stays clean and the pool remains protected during the cold months. The process begins with thoroughly cleaning the pool by vacuuming, brushing the walls and floor, and balancing the water chemistry. Chlorine levels should be adjusted to a proper winterizing level, and algaecide is often added to prevent growth under the cover. Covering the pool effectively with a durable winter cover is essential to keep out leaves, dirt, and precipitation.
Next, all pool equipment must be winterized. This includes draining water from the pump, filter, and heater to prevent freezing and cracking. Using pool antifreeze in the plumbing lines adds another layer of protection against cold temperatures. Plugs are also inserted into the return jets and skimmer to keep cold water from damaging the plumbing system. Following these steps will help protect your investment and make reopening the pool in spring much easier and less time-consuming.
What type of cover should be used when leaving water in the pool over winter?
When leaving water in a pool over winter, it’s critical to use a strong, durable cover specifically designed for winter conditions. Solid winter covers and mesh safety covers are the two main options. A solid cover provides a barrier that prevents debris and water from penetrating into the pool while a mesh cover allows water to drain through, reducing the chance of standing water accumulation but allowing more debris through to the pool floor.
The choice between the two depends on your climate and the likelihood of heavy rain or snowfall. In regions with heavy precipitation, a mesh cover may help prevent excessive water buildup that could strain the cover or damage the pool. A solid cover is often better at keeping the pool clean but may require a pump or manual removal of rain or melted snow. Regardless of the type, it should be secured tightly using water bags or springs to keep out contaminants and protect the water beneath it.
Can pool antifreeze help protect water left in the pool during winter?
Pool antifreeze can be an effective tool for protecting plumbing lines when water is left in the pool over winter, especially in colder climates. It is typically used to prevent residual water in the pipes from freezing after the filtration system has been drained and closed down. Pool antifreeze is non-toxic and designed specifically for this purpose, usually made from propylene glycol, which lowers the freezing point of any remaining water in the lines and helps prevent freeze damage.
However, pool antifreeze should not be used to protect the main body of water in the pool or replace proper winterization steps. Its purpose is limited to safeguarding plumbing lines and equipment during freezing temperatures. It’s important to never mix pool antifreeze with automotive antifreeze, which is toxic. When used correctly, antifreeze can help preserve your equipment and ensure a smoother opening process when reactivating your pool in the spring.
What should you do if the water level drops in a winterized pool?
If the water level in your winterized pool drops, it may indicate evaporation, heavy rain runoff, or a potential leak. Begin by inspecting the cover and surrounding area for signs of damage or improper sealing. If water has collected on top of the cover, remove it promptly using a sump pump or cover pump to prevent strain on the cover and avoid the risk of debris being pushed through into the pool water.
If the cover remains intact, the drop in water level is usually not an immediate concern as long as the water is below the skimmer and tile line. However, if the water gets too low and exposes the pool surfaces, especially in in-ground pools, it could lead to cracking or staining from dry areas. Using water bags or a floating cover to keep the water level high enough to protect surfaces is a common solution. Always ensure your cover remains securely fastened to avoid further issues and check on the pool periodically throughout winter.