Keeping your swimming pool in optimal condition requires more than just regular cleaning and chemical balancing. One of the most effective ways to protect your pool is by using a pool cover. However, many pool owners are unsure about what to place under the cover to maximize its benefits. Whether you’re using a solid winter cover, a solar cover, or a safety cover, what you place beneath it can significantly impact the effectiveness of your winterization or maintenance efforts.
In this in-depth guide, we’ll explore what should and shouldn’t go under a pool cover, why it matters, and how to optimize your pool care routine through proper preparation under the cover. We’ll also break down the different types of pool covers and the appropriate undercover elements for each.
Understanding Pool Covers: Types and Purposes
Before diving into what goes under a pool cover, it’s crucial to understand the different types of covers and their intended purposes. Each cover requires specific care and preparation under it to function effectively.
1. Solid Winter Pool Covers
Solid winter pool covers are typically used in colder climates to protect the pool during the off-season. Designed to prevent debris, precipitation, and small animals from entering the water, they are often the most robust and heavy-duty option.
2. Solar Pool Covers
Also known as thermal blankets or solar blankets, these covers are designed to absorb sunlight and retain heat. They float on the water surface and help reduce evaporation, thereby conserving energy and maintaining water temperature.
3. Safety Pool Covers
Safety covers are made to provide a secure barrier over the pool when not in use, especially during winter. Many are reinforced with straps and anchors to support the weight of snow and debris. These covers are often installed slightly above the water level.
4. Automatic and Mesh Pool Covers
Automatic pool covers are motorized systems that offer convenience and enhanced safety. Mesh covers, on the other hand, allow water to drain through them while keeping debris out. They are typically used during the summer season or in moderate climates.
What to Place Under a Pool Cover: By Type
The items you place under a pool cover depend on the type of cover, the season, and whether the pool is being closed for winter or maintained during the swimming season.
1. For Winter Pool Covers
Winter covers are the most common type for seasonal closure. To prepare your pool correctly for winter, the following items may be placed under the cover:
- Precision winterizing chemicals – Including algaecide, winterizing kits, and chlorine or non-chlorine shock.
- Winterizing plugs – Installed in return jets and skimmers to prevent water from freezing in the lines.
- Pool cover pump – A critical tool to remove standing water that accumulates on top of the cover.
- Aquatic cover balls (also known as air pillows) – These protect the pool structure from ice expansion by allowing space for water to push upward when freezing.
Chemical Treatment Before Closing
Balancing your pool water chemistry before closing it for winter is essential. The key parameters to check include:
| pH Level | 7.2–7.6 |
|---|---|
| Alkalinity | 80–120 ppm |
| Calcium Hardness | 200–400 ppm |
| Chlorine | 0–1 ppm (after shocking) |
Use a winter algaecide and chlorine or potassium monopersulfate (non-chlorine shock) to eliminate potential contaminants. This step prevents algae growth and corrosion underneath the cover.
Water Level Considerations
When placing a solid winter cover over a pool, the water level should typically be at or slightly below the skimmer. This helps prevent freeze damage from expansion.
However, if you install a cover pillow or air pillow, you’ll want the water level high enough to submerge the pillow while allowing space for expansion. The cover should sit slightly above the water, not submerged, to ensure proper placement and performance.
2. For Solar Covers
Solar pool covers are not designed to be completely sealed or require winterizing chemical treatments. Instead, the focus is on maintaining temperature and minimizing evaporation. Since these covers remain in place during the swimming season, the following items may go under or around the cover:
- Proper water balance – Crucial for swimmer comfort and to prevent scaling or corrosion.
- Skimmer sock or basket – Helps catch fine debris that might otherwise float on the pool cover.
- Chlorine or bromine tablets – Some owners place floating chlorinators or erosion feeders under the solar cover to help the chemicals disperse evenly.
However, some automatic chlorinators or tablet feeders should not be used under a solar cover, especially if the cover is removed and replaced regularly, as this can trap chlorine gas and degrade the cover material.
How to Use a Solar Cover Correctly
A solar cover should be applied with the bubble side down, as this allows the bubbles to absorb sunlight and transfer heat to the water. It should be trimmed to fit the pool shape, allowing full coverage without frayed or hanging edges.
Avoid placing heavy objects directly on solar covers as they can puncture or damage the material. Additionally, do not leave covers on for extended periods when the pool is not in use; instead, use when aiming to warm the water or maintain a clean surface.
3. For Safety Pool Covers
Safety pool covers are often the strongest type, designed to support weight and create a secure barrier above the water. Because these covers are usually installed a few inches above the waterline, you typically don’t place anything directly underneath the cover during installation.
However, proper closure of the pool involves:
Pre-Winter Water Balance
As with solid covers, water chemistry must be balanced before closing the pool. Proper sanitation and stabilizing minerals like calcium and alkalinity protect the pool surface and water quality during winter.
Pipe and Equipment Winterization
Ensure all plumbing lines are cleared of water, and the pump, filter, and heater are winterized (pumped dry or filled with antifreeze). Safety cover edges are secured using anchors around the pool perimeter.
4. For Mesh Pool Covers
Used during the swimming season or in moderate winter climates, mesh covers allow rain and snowmelt to drain through while keeping large debris out. What you place underneath should follow many of the same practices used with solid winter covers.
Chemical Treatment
Despite allowing water to pass through, mesh covers still require careful chemical balancing before cover installation. Since pools under mesh covers remain closed for weeks or months, preventing algae growth and corrosion is essential.
Cleaning Elements
Before installing a mesh cover, perform deep cleaning routines:
- Brush pool walls and floor
- Vacuum pool thoroughly
- Check and empty skimmer baskets and pump baskets
Since mesh covers do not totally seal the pool, ensure that steps are taken to minimize debris accumulation over the winter. This helps reduce spring opening efforts.
Additional Tips for Preparing Under the Cover
To help pool owners make informed decisions about what to put under a cover for optimal results, here are some key tips and considerations.
1. Use Chemical-Dosing Tools Strategically
Automatic feeders or dissolving tablets should only be used under summer-use covers like solar blankets. Under winter covers, especially solid or mesh options, chemical feeders are ineffective and can even cause damage when left for long periods.
2. Prevent Algae Growth with Algaecide
Adding a dose of winter algaecide under the pool cover is essential, particularly in regions with inconsistent freezing. Even with a high-quality cover, some sunlight can penetrate underneath, feeding algae growth.
3. Water Level Management
The appropriate water level varies depending on the type of cover:
| Cover Type | Water Level | Notes |
|---|---|---|
| Solid Winter Cover | Slightly below skimmer, with cover pillow under the cover | Prevents ice from damaging the pool walls |
| Mesh Winter Cover | At water line or with slight cover pillow | Drainage helps prevent excess weight |
| Solar Cover | Full pool water level | Water must touch the cover to absorb solar energy |
| Safety Cover | 3–5 inches below skimmer | Typically installed above the water surface |
4. Avoid Overheating Under Solar Covers
Under solar covers, excessive heat can lead to chemical imbalance. It’s important not to allow the cover to remain in place unchecked if the pool is not being used regularly. Monitor the water temperature and remove the cover when not needed to maintain proper circulation and treatment.
5. Regular Maintenance of Pool Covers
Pool covers themselves need periodic maintenance to ensure they perform well both over and under the water. For winter covers:
- Clean debris regularly from the top
- Use a cover pump to remove standing water
- Check straps and anchors for tension and wear
For solar covers:
- Roll or fold correctly to prevent tears
- Store out of direct sunlight when not in use
- Inspect for UV degradation and holes
6. Don’t Use Covers as a Substitute for Proper Filtration and Cleaning
A common misconception is that placing a cover eliminates the need for chemical treatment and cleaning. In reality, proper maintenance must happen before the cover is placed, not just after. Even with the best pool cover, neglecting preparation can lead to water clarity issues, scaling, and even structural damage.
What Not to Put Under a Pool Cover
Just as it’s important to know what to place under the cover, it’s equally important to understand what not to place under it.
- Heavy objects directly on the cover surface – They can puncture or damage the material and disrupt water chemistry balance.
- Improper winterizing chemicals – Using the wrong concentration or type of winterizing solution can damage the pool finish and equipment.
- Live animals or plants – While it may sound extreme, some pools are left with decorative fish; these should be removed to prevent deaths and ammonia buildup in the water.
- Non-approved chemical feeders – Some automatic feeders will continue dispensing chemicals over months, which can corrode internal components and negatively impact water balance.
- Loose debris or leaves – Never allow leaves to accumulate under a closed cover. Do a final vacuum before closing and remove all floating debris.
If you’re in a region with seasonal weather shifts, always follow a closing checklist tailored to your climate and pool configuration. This includes a professional pool inspection or consultation if you’re new to winterizing procedures.
Why What You Place Under the Cover Matters
Taking the time to understand the role of your pool cover and properly preparing what goes underneath can extend the lifespan of your pool and reduce the workload of opening it again in spring. Whether you’re protecting against contaminants, maintaining chemical clarity, or safeguarding against ice damage, thoughtful preparation pays long-term dividends.
In colder climates, improper winterization can lead to algae blooms, staining, or even cracked tiles due to pressure from ice expansion. In warmer climates, failing to properly maintain temperature and sun protection can lead to increased water evaporation and chemical loss.
Conclusion: Proper Preparation Equals Protection
Choosing the right items to place under your pool cover is more than just a routine chore—it’s an investment in the long-term health and beauty of your pool. The materials you decide to install, the chemicals you use, and even the position of the water level all contribute to a successful pool cover application.
To recap:
- Balance water chemistry before applying any cover
- Use an appropriate amount of algaecide
- Drain and winterize all equipment
- Place cover correctly—consider using a cover pump if you use a solid or mesh model
- Choose accessories and tools that are cover-compatible
By incorporating these practices into your seasonal pool maintenance schedule, you’ll enjoy a cleaner, safer, and longer-lasting pool structure—no matter the time of year.
Whether you’re prepping for a long winter or simply trying to enhance your pool’s energy efficiency with a solar blanket, a little planning under the cover now can make all the difference when it’s time for a fresh dip later.
So, next time you prepare to cover your pool, ask yourself: What do I put under pool cover? — and prepare accordingly.
What is the purpose of using a pool cover?
A pool cover serves several important purposes for pool owners, helping to maintain water quality, reduce chemical usage, and protect the pool when it is not in use. Depending on the type of cover, it can prevent debris, such as leaves, dirt, and insects, from entering the water, which minimizes the effort required for cleaning and maintenance. Additionally, it can help retain heat in the pool, especially with solar covers, and reduce evaporation, which helps conserve water and maintain proper chemical balance.
Safety and environmental considerations are also key functions of a pool cover. Safety covers, for instance, are designed to support weight and prevent accidental falls into the pool, making them essential for families with children or pets. Covers also shield the pool from harsh weather such as heavy rain or snow, thereby preventing damage. Overall, using the right pool cover contributes significantly to the longevity and usability of a swimming pool.
What are the different types of pool covers available?
There are several types of pool covers designed for specific purposes, including safety covers, solar covers, winter covers, and automatic covers. Safety covers are heavy-duty and designed to prevent accidents by supporting weight, making them ideal for residential pools where children or pets are present. Solar covers are lighter, made from UV-resistant material, and designed to trap heat and reduce water evaporation, helping to keep the pool warm and reduce heating costs.
Winter covers are used primarily during the off-season to protect the pool from debris and weather damage. They are usually made from heavy-duty, durable material that can withstand cold temperatures and snow. Automatic covers, on the other hand, are motorized systems that can be rolled on and off the pool with the push of a button. Choosing the right type of pool cover depends on your specific needs—whether for safety, temperature control, seasonal protection, or convenience.
What should you put under a pool cover?
Under a pool cover, it’s important to place materials that help maintain pool cleanliness, protect the cover itself, and aid in proper water chemistry when the pool is not in use. Pool owners often use pool cover support systems or air pillows to prevent water and snow from accumulating directly on the pool surface, which could damage the cover or the pool walls. These supports help distribute the weight evenly and allow the cover to do its job effectively.
Some pool owners may also choose to place chemical dispensers or winterizing kits beneath solid winter covers to ensure that the water remains balanced during the off-season. However, it’s important to avoid placing any unnecessary objects or loose materials under safety or solar covers, as this can interfere with their function or pose a safety risk. Always follow the manufacturer’s recommendations and consult a pool professional when in doubt.
Why should an air pillow be used under a pool cover?
An air pillow is used under a pool cover—especially during winter—to act as a buffer between the cover and the pool water, preventing damage from hydrostatic pressure and ice expansion. When water freezes, it expands, which can put stress on pool walls and the cover. By placing an inflated air pillow on the surface of the water before covering, pool owners create a space for the ice to press against without damaging the pool structure or putting undue tension on the cover.
Air pillows also help reduce the risk of the cover sinking too far into the pool or collapsing under the weight of snow and ice. This helps prevent water from accumulating on top of the cover and ensures it remains functional throughout the winter. Proper placement and inflation of air pillows are essential for optimal performance, and they should be compatible in size and shape with your particular pool setup.
Are there items that should never be placed under a pool cover?
Yes, there are certain items that should not be placed under a pool cover, as they can compromise water balance, damage the pool surface, or interfere with the cover’s function. Avoid placing heavy or sharp objects, such as rocks, metal tools, or furniture, under the cover, as they can puncture or tear the bottom of the cover and scratch the pool liner or walls. Similarly, avoid using excessive amounts of pool chemicals directly under the cover that are not in dispensing systems, as concentrated chemical contact may cause staining or damage.
In addition, wooden boards, pool noodles, or makeshift supports should not be used in place of proper air pillows or support systems. These materials are not designed for this purpose and may not provide adequate protection against ice expansion or water accumulation. Instead, opt for products specifically designed for under the pool cover, such as winterizing chemical kits and purpose-made air pillows, to ensure both the cover and the pool remain in good condition.
How do you prepare your pool before placing a cover?
Before placing a pool cover, it’s essential to properly clean and treat the pool to ensure the water remains balanced and the equipment is protected during the covered period. Begin by skimming the surface and vacuuming the bottom to remove any debris. Use a pool brush to scrub the walls and tile line to eliminate algae or buildup. Once the pool is clean, test the water chemistry, adjusting pH, alkalinity, and chlorine or bromine levels to prevent algae growth and maintain clear water.
If you’re using a winter cover, it’s important to add winterizing chemicals to the water as directed, which will keep the pool sanitized for the off-season. Lower the water level appropriately if necessary, depending on your cover type and climate conditions. Install an air pillow if needed, and make sure any pool equipment, such as pumps and heaters, is properly winterized or turned off. Once your preparations are complete, carefully place the cover over the pool, securing it tightly to prevent shifting or water accumulation on top.
How do you maintain a pool cover and the area underneath?
Proper maintenance of a pool cover and the area beneath it is crucial to prolong its life and protect the pool effectively. Start by checking the cover regularly for signs of wear, such as tears or sagging, especially after heavy rain or snowfall. Clean any debris or standing water from the surface of the cover using a soft brush or manual siphon to prevent damage and mold growth. If your cover has a drain system, ensure it remains unobstructed and functional throughout the period it is in use.
Underneath the cover, it’s important to maintain balanced water chemistry. If you’ve winterized your pool, test the water occasionally if possible, or rely on chemical doses that are designed to last through the off-season. Inspect air pillows or support systems regularly to ensure they remain properly inflated and positioned. If you’re using a safety cover, ensure the tensioning springs or anchors remain tightened and secure. By performing regular maintenance checks, pool owners can ensure their cover continues to protect the pool efficiently until it’s time to open it again.