Antifreeze is often used during the winterization process to protect a pool’s plumbing system from freeze damage in cold climates. While some pool service technicians rely heavily on antifreeze as part of their winterization strategy, others use alternative methods like blowing out the lines with compressed air. Here’s a breakdown of the pros and cons of using antifreeze when winterizing a pool, to help you determine whether it’s the right choice for a particular situation.

Pros of Using Pool Antifreeze

• Extra Layer of Protection Against Freezing Antifreeze provides an added layer of defense for the pool’s plumbing. Even if some water remains in the lines after they’ve been blown out, antifreeze can prevent any residual water from freezing, expanding, and causing pipes to crack or burst. This can be particularly useful in regions where temperatures drop below freezing for extended periods.

• Key Benefit: Acts as a fail-safe in case water is trapped in hard-to-reach spots in the plumbing system.

• Effective for Complex Pool Systems Pools with more complex plumbing layouts — such as those with multiple return lines, water features, or attached spas — may have areas where it's difficult to completely remove water by blowing out the lines. In these cases, antifreeze ensures protection for those hard-to-drain areas.

• Key Benefit: Provides peace of mind in pools with complicated plumbing where removing all water may not be possible.

• Simple to Use Antifreeze is easy to add to the plumbing lines. Simply pour the antifreeze into the skimmers or directly into the return lines and let it flow into the system. There’s no need for specialized equipment beyond basic tools, making it an accessible option for pool service technicians.

• Key Benefit: Straightforward and quick to apply, especially for smaller pools or simpler systems.

• Non-Toxic Formulas Available Pool antifreeze is different from automotive antifreeze. It’s typically formulated with non-toxic propylene glycol, making it safe for use in pools and less harmful to the environment when it needs to be flushed in the spring. This non-toxic formula also means it’s safer for humans and animals. It is designed to break down harmlessly when diluted into the pool water during spring reopening.

• Key Benefit: Non-toxic and safer for residential and commercial use.

• Prevents Potential Residual Water Damage If compressed air doesn’t remove all water from the lines (common in older plumbing systems), antifreeze can prevent residual water from freezing. This is especially helpful when a pool tech isn’t confident about getting every last drop out of the system.

• Key Benefit: Provides additional security against undetected water in pipes.

Cons of Using Pool Antifreeze

• Not a Substitute for Blowing Out Lines While antifreeze helps protect against freezing, it should not be used as a substitute for blowing out the lines with compressed air. Relying solely on antifreeze without removing water from the lines increases the risk of freeze damage, especially in larger pools. The primary winterization technique should always be to remove as much water as possible.

• Key Drawback: It cannot fully prevent freeze damage if water is left in large amounts within the plumbing system.

• Can Be Messy and Difficult to Flush Out When it’s time to reopen the pool in the spring, the antifreeze must be flushed out of the plumbing system. If not properly removed, antifreeze can cause water quality issues and interfere with pool chemistry. While non-toxic antifreeze won’t harm swimmers, it can cause temporary foaming or affect water clarity until it's filtered out. Additionally, flushing antifreeze from long runs of plumbing can be messy and time-consuming.

• Key Drawback: Can create additional work when reopening the pool, especially in larger systems.

• Cost Using antifreeze for winterizing Antifreeze

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adds an extra expense to the pool closing process. The cost can be significant, especially for larger pools with extensive plumbing systems. For smaller pools or those in less severe climates, the added cost may not be justifiable, particularly if the lines can be fully blown out with compressed air.

• Key Drawback: May be an unnecessary cost in areas where freezing temperatures are rare or minimal.

• Not Always Necessary In many climates, especially those with milder winters, properly blowing out the lines with air pressure can be sufficient. If all the water is removed, antifreeze becomes redundant. Some technicians prefer not to use antifreeze unless absolutely necessary, to avoid the extra step of cleaning it out in the spring.

• Key Drawback: Unnecessary in regions with mild winters or for pools with simple plumbing setups.

• Environmental Concerns Although most pool antifreezes are formulated to be non-toxic, using large amounts of antifreeze can still raise environmental concerns. If not handled and disposed of properly, antifreeze can end up in local water systems or the soil. While it's less harmful than automotive antifreeze, it’s still important to follow proper disposal guidelines to minimize environmental impact.

• Key Drawback: Improper disposal or excessive use can have a negative environmental impact.

• Potential for Dilution If any water remains in the plumbing lines before adding the antifreeze, it can dilute the antifreeze and reduce its effectiveness. This is particularly an issue in regions with early freezing conditions, where water may already be present in the lines. This dilution can lead to incomplete protection and potential damage.

• Key Drawback: Diluted antifreeze may not provide adequate freeze protection.

When to Use Antifreeze

Antifreeze is most beneficial in certain situations:

• Severe Cold Climates: If you're winterizing a pool in an area that experiences long periods of subfreezing temperatures, antifreeze can provide added security.

• Complex Plumbing Systems: Pools with intricate layouts, multiple lines, or water features are more likely to trap water, making antifreeze a useful safeguard.

• Older Pools: Older pools with plumbing that may not be as airtight or efficient at draining can benefit from the extra layer of protection antifreeze provides.

When Antifreeze May Not Be Necessary

• Mild Climates: In areas where the winters are mild and rarely dip below freezing, properly blowing out the lines may be sufficient without the need for antifreeze.

• Smaller Pools: In small, simple pools where all the plumbing lines can be easily cleared, antifreeze might not be necessary.

• Cost-Sensitive Jobs: For clients on a tight budget, antifreeze may not be an essential expense if other winterization steps are performed correctly.

Using antifreeze during pool winterization has clear advantages, particularly as an extra layer of protection for plumbing in cold climates. However, it’s important to remember that antifreeze should complement, not replace, the process of blowing out lines. While it can be a useful tool for preventing freeze damage, antifreeze is not always necessary and can add costs and extra work when reopening the pool in the spring.

It's important to remember that antifreeze isn’t removed from the water during spring opening — it’s diluted into the pool and gradually filtered out. While this doesn’t pose a health risk with non-toxic antifreeze, pool techs must still ensure water chemistry is properly adjusted afterward.