Protecting your swimming pool during the winter months is essential to avoid costly damage from freezing temperatures. One of the many questions that arise during the winterization process is whether to put antifreeze in the skimmer. This article will explore this topic in depth—covering the why, the how, and the what happens if you don’t. By the end, you’ll have a clear understanding of whether antifreeze belongs in your skimmer and how to make the best decisions for your pool’s long-term health.
Purpose of Antifreeze in Pool Winterization
Winterizing a pool involves several steps aimed at protecting the equipment and structure from damage caused by freezing weather. While draining most of the water and using winterizing chemicals are well-known steps, the use of antifreeze specifically in the skimmer is often misunderstood or overlooked.
Antifreeze in a pool isn’t the same as the kind you use in your car. Pool antifreeze is non-toxic, typically made from propylene glycol, and designed to protect water lines and plumbing from freezing. Its purpose is to displace water in the plumbing lines and skimmers to prevent ice from expanding and cracking components.
Can Water Freeze in the Skimmer?
Yes—and here’s why: the skimmer is an open component connected to the pool’s plumbing system. Even after you drain the water to the proper level (below the skimmer, jet inlets, and returns), some water will remain in the skimmer throat or the connected pipes. If this residual water freezes, it can crack the skimmer housing or pipes, leading to expensive repairs come springtime.
Choosing the Right Type of Antifreeze
Not all antifreeze products are safe or suitable for use in pools. There are two common types:
- Ethylene glycol-based antifreeze: Highly toxic and not recommended for use in pool systems.
- Propylene glycol-based antifreeze: Non-toxic and specifically designed for pool and plumbing use.
Always double-check the product label and ensure it is compatible with pool plumbing. Using the wrong kind can be dangerous and degrade plastic components in your system.
Step-by-Step Guide: How to Use Antifreeze in the Skimmer
Knowing whether to use antifreeze in the skimmer leads to the next question: How do you do it? Below are the recommended steps for using antifreeze in your skimmer effectively and safely.
Step 1: Drain the Water Level Below the Skimmer
The first and most critical step in winterizing your pool is lowering the water level. You should drain the water to approximately 6 to 8 inches below the skimmer. This prevents standing water in the skimmer basket area from freezing.
Step 2: Remove any Debris or Components
Clean the skimmer and remove the skimmer basket and weir door (if applicable). Leaving these components in place can trap water and lead to cracks or damage after the glycol freezes or exerts pressure.
Step 3: Blow Out the Skimmer Line
Before adding antifreeze, always use an air compressor or shop vac to blow out the skimmer line. While this process won’t remove every last drop of water, it clears a significant amount—reducing the amount of antifreeze you’ll need.
Tip: Never use compressed air directly into the pool if the pump is still installed as this may cause damage.
Step 4: Add the Antifreeze to the Skimmer
Once the line is partially cleared, pour enough pool antifreeze into the skimmer so it fills the remaining portion of the throat and moves into the plumbing. As a general rule, a quart of antifreeze should suffice for most skimmer lines. The liquid will fall into the pipe, displacing the remaining water and lowering the risk of freeze damage.
Step 5: Seal the Skimmer Properly
To prevent backflow and keep water from entering the skimmer during winter, insert a skimmer plug (some are foam-based, others are threaded) and use a skimmer cover or cap. These help keep moisture and debris out.
Pro Tip: Don’t forget to add antifreeze to other plumbing lines in your pool system, including return jets and the main drain line (if closed before winter).
When Is Antifreeze in the Skimmer Necessary?
You might wonder whether you need to use antifreeze in your skimmer at all. That depends on the climate where you live and the winterization method you’ve used.
Climate Considerations
If you live in an area where winter temperatures regularly fall below freezing (32°F or 0°C), using pool antifreeze is almost always necessary for complete winter protection. In milder climates, with only occasional freezing, you might get by with just blowing out the lines and lowering the water level—but it’s not as safe.
Drain vs. No-Drain Winterization?
There are two primary winterization strategies: the drain method and the no-drain (float) method. In the no-drain method, a special winter cover and air pillow are used to create space in the middle of the pool for expanding ice. If you don’t drain the pool water significantly, you’ll likely need more extensive use of antifreeze in both skimmers and returns.
Pool Type and Equipment
Above-ground pools often require fewer lines and less antifreeze than in-ground pools, especially those with complex plumbing systems (multiport valves, heaters, chlorinators, etc.). It’s essential to evaluate your specific setup and whether it leaves residual water in the skimmer or surrounding pipes.
Alternatives to Using Antifreeze in the Skimmer
Using pool antifreeze isn’t the only way to protect your skimmer from freezing. Other methods include using compressed air, installing freeze-protect devices, and using insulating covers, but they all come with pros and cons.
Air Compressor or Blower Method
As mentioned earlier, this method involves blowing water out of the skimmer pipe using a shop vac or low-pressure compressor. While effective, it can be difficult to remove every drop of water—leaving the skimmer vulnerable during deep freezes.
Insulating Covers and Foam Plugs
Foam skimmer plugs and insulated skimmer covers provide a secondary defense against freezing. They are best used as a companion to antifreeze—not a replacement. These items help to reduce heat transfer and slow the freezing process within the skimmer.
Freeze Protection Valves and Sensors
For pools with automation, freeze sensors can be installed. These systems automatically start the pump during freezing conditions to keep water circulating and reduce ice formation. However, this only works if the system isn’t reliant on a closed plumbing line and doesn’t provide a complete guarantee against damage.
Comparing Methods: Blowouts vs. Antifreeze vs. Sensors
| Method | Effectiveness | Cost | Effort Required |
|---|---|---|---|
| Blowouts (Compressed Air) | Moderate | Low | Moderate |
| Pool Antifreeze | High | Moderate | Low to Moderate |
| Freeze Protection Sensors | High (with proper setup) | High | Low |
| Insulating Covers + Foam Plugs | Low to Moderate | Low | Low |
While each option can prevent freeze damage, combining methods—such as using pool antifreeze and a foam skimmer plug—offers the best protection for in-ground pool systems in colder climates.
What Happens If You Forget Antifreeze in the Skimmer?
If antifreeze isn’t used in the skimmer in freezing conditions, ice can develop in the skimmer throat or connecting pipes. Water expands as it freezes, leading to what could be catastrophic damage.
Skimmer Throat Cracks
A crack in a fiberglass or plastic skimmer is a common result of improper winterization. Repairing or replacing a cracked skimmer can cost several hundred dollars—and many pool owners are caught off guard during the spring startup when leaks appear.
Pipe Damage
Plastic PVC pipes can also crack from ice expansion. Repairing broken lines often requires excavation in serious cases, increasing costs significantly.
Long-Term Consequences
Even a small amount of pipe cracking can lead to poor circulation, chemical imbalance, and long-term structural problems. The cost of repairs and extended downtime far outweighs the modest cost of pool antifreeze.
Best Practices for Winterizing Your Pool: Including the Skimmer
If you’re looking to go beyond one step, adopting a complete winter protocol ensures your pool survives the season unharmed.
Add Winter Algaecide
Killing off algae before winter is crucial to prevent staining and overgrowth when warmer weather returns.
Balance Your Pool Water
Properly balancing your water chemistry (especially pH, alkalinity, and calcium hardness) prevents scaling, corrosion, and staining.
Use a Winter Pool Cover
A secure, durable cover keeps debris and melting snow from contaminating your pool. Some covers are heavier and designed for winter use only.
Drain Equipment and Install Plugs
Besides the skimmer, your pump, filter, and heater should be fully drained, and plugs installed in all threaded openings. Use expanding foam or rubber freeze plugs in non-threaded lines.
Complete Final Inspection
Before leaving your pool for the season, do a final walk-around. Look for:
- Any unsealed lines
- Areas with pooled water
- Missing skimmer plugs or air pillows
- Proper winter cover tension
Final Thoughts: Should I Put Antifreeze in My Skimmer?
The answer is yes—if you’re preparing your pool for winter in a climate where freezing temperatures are expected.
Using propylene glycol-based antifreeze in your skimmer is a smart, cost-effective preventive measure that can greatly reduce your chances of needing costly repairs in the spring. While other methods like blowouts or foam plugs may provide some protection, combining techniques ensures your pool survives the winter in proper working condition.
Remember: The minimal cost of pool antifreeze pales in comparison to the cost of cracked skimmers or broken plumbing. Your winter protection efforts today will pay off next summer with a smooth pool opening and more swimming time!
Conclusion and Winterization Checklist
Before you close your pool for the season, print and follow this handy checklist:
- Test and balance pool water.
- Clean the pool thoroughly (brush walls and vacuum).
- Add winter algaecide and shock the pool.
- Drain water level 6–8 inches below the skimmer.
- Blow out skimmer and return lines.
- Pour pool antifreeze into the skimmer and returns.
- Install threaded or foam winter plugs in all lines.
- Place an air pillow in the center of the pool (if applicable).
- Secure a winter cover tightly over the pool.
- Protect equipment by draining, adding antifreeze, and covering.
Investing time and effort now is the key to protecting your pool’s future—so you can open it quickly and confidently when the warmer weather returns.
Don’t overlook the skimmer when winterizing your pool—one simple step can prevent a lot of pain (and expense) later on.
Can I put antifreeze in my pool skimmer to winterize my pool?
Yes, you can put antifreeze in your pool skimmer as part of the winterization process, but it’s important to do it correctly. This method is typically used to protect the skimmer and the plumbing lines from freezing temperatures. However, not all types of antifreeze are safe for pools. You must use non-toxic, pool-safe antifreeze specifically designed for this purpose. Automotive antifreeze is highly toxic and can damage your pool components and pose health risks.
To properly use antifreeze in the skimmer, you should first drain as much water as possible from the lines. Then, blow the lines clear using a compressor and insert the proper amount of antifreeze into the skimmer. This ensures that any remaining water in the plumbing won’t freeze and expand, which can cause cracks and costly damage. Always consult your pool’s manufacturer guidelines or a professional if you’re unsure about the best method for your specific setup.
Why is winterizing a pool important?
Winterizing a pool is crucial to protect it from the damaging effects of freezing temperatures. When water freezes, it expands, which can cause cracks in the pool structure, plumbing lines, and equipment like the pump and filter. By properly winterizing your pool, you ensure that the water chemistry remains balanced, surface damage is minimized, and equipment lasts longer, making it easier to open the pool in spring.
The process also keeps debris and contaminants from building up over the off-season, which can lead to staining and algae growth. Covering the pool properly after winterization helps maintain water quality and prevents leaves, dirt, and animals from getting into the water. This not only saves time and effort in the long run but also protects your investment and ensures your pool is in good condition when you’re ready to use it again.
What type of antifreeze should I use in my pool skimmer?
Only non-toxic, pool-safe antifreeze should be used in a pool skimmer during winterization. This type of antifreeze is typically made from propylene glycol, which is safer than ethylene glycol-based automotive antifreeze and won’t harm your pool’s plumbing or equipment. It’s formulated to protect against freezing without contaminating the water or posing a risk to people, pets, or wildlife.
Choosing the right product is essential for both safety and effectiveness. When purchasing antifreeze for your pool, read the label carefully to confirm it is labeled as “pool-safe” or “non-toxic.” Avoid using any kind of automotive antifreeze, as it can be extremely dangerous if it enters the pool water. Additionally, pool-safe antifreeze is compatible with the materials used in pool plumbing systems, ensuring no long-term damage occurs during storage.
How much antifreeze should I put in the skimmer?
The amount of antifreeze needed in the skimmer typically depends on the length and diameter of the plumbing lines being protected. A general guideline is to use about one quart of antifreeze for every 10 feet of 1.5-inch diameter pipe. To ensure accuracy, it’s best to calculate the total volume of the plumbing lines from the skimmer to the pump or main drain.
Pour the antifreeze slowly into the skimmer to allow it to travel through the pipes and displace any remaining water. You should also pour antifreeze into the main drain line if your system includes one. Be careful not to overfill, as this can lead to spillage and potential damage to surrounding areas. Always wear gloves and eye protection when handling and disposing of antifreeze, and store unused product properly.
Can I skip using antifreeze if I blow out the lines?
Yes, you can skip using antifreeze if you completely blow out the plumbing lines with a compressor during the winterization process. Line-blowing is a common method that uses air pressure to expel all standing water from the pipes, reducing the risk of freezing. However, this method requires proper technique and the right equipment to ensure every part of the plumbing system is fully dry.
Even if you blow out the lines, some professionals still recommend adding a small amount of antifreeze as a precaution in case pockets of water remain. Trapped water can freeze and cause cracks, especially in cold climates. If you’re confident in your ability to thoroughly blow out the lines and have done so with past success, antifreeze may not be necessary. Otherwise, using it provides an added layer of protection to safeguard your pool plumbing.
What are the risks of using automotive antifreeze in a pool skimmer?
Using automotive antifreeze in a pool skimmer is extremely dangerous and not recommended. Automotive antifreeze usually contains ethylene glycol, which is highly toxic and can be harmful or even fatal if ingested by humans or animals. If this type of antifreeze leaks into the pool water, it poses serious health risks and can complicate the opening process in the spring, requiring extensive cleaning and chemical balancing.
In addition to health hazards, automotive antifreeze can damage your pool’s plumbing, seals, and equipment over time due to chemical incompatibility. It may degrade materials like PVC, rubber gaskets, or plastic components, leading to leaks or costly repairs. Always use a non-toxic, pool-safe antifreeze specifically designed for winterizing pools. Taking shortcuts with automotive products endangers safety and may void equipment warranties.
What other steps should I take to winterize my pool?
Winterizing a pool involves several important steps beyond adding antifreeze to the skimmer. Begin by thoroughly cleaning the pool and adjusting the chemical balance, usually by lowering the pH slightly and adding a winterizing algaecide. Drain the water level below the skimmer opening, following manufacturer guidelines for your specific pool type. Remove all equipment, including the pump, filter, and heater, and store them indoors to prevent freezing.
Next, blow out and/or plug the plumbing lines and add antifreeze if necessary. Install a winter pool cover securely to prevent debris and water accumulation, and consider using water balance testing kits before closing the pool. Filling a few gallons of water into the cover to weigh it down (for solid covers) or using safety nets ensures secure placement during wind and snow. Proper winterization ensures your pool equipment and structure resist winter’s harsh effects and remain in good condition for the next season.