Advanced Oxidation Process for Swimming Pools

An AOP system uses a combination of oxidizers — often UV light, ozone, and/or other treatments- to generate hydroxyl radicals (·OH) that rapidly neutralize contaminants in pool water. These radicals are among the most powerful oxidizers used in water treatment, and they work faster and more thoroughly than standard sanitizers.

In simple terms, water is circulated through a specialized AOP reactor after filtration. Inside, the system uses UV and/or ozone (or other oxidizer methods, depending on the design) to generate hydroxyl radicals. These radicals immediately attack and break down organic matter, bacteria, chloramines, and many other pollutants — resulting in cleaner, clearer water without relying solely on chlorine or other traditional sanitizers.

AOP oxidizes both organic and inorganic impurities—such as oils, lotions, body residues, chloramines, biofilm precursors, and microscopic organics. Many of these are managed slowly or poorly by chlorine alone.

Because hydroxyl radicals react rapidly and with many substances, AOP helps clean water of contaminants that cause cloudiness, odors, irritation, and lingering organics. The result is pool water that looks clearer, smells fresher, and feels more natural compared to typical chlorine treatment.

AOP significantly reduces the burden on chlorine, but in most residential pools, it does not eliminate the need for a residual sanitizer such as chlorine. Hydroxyl radicals oxidize contaminants during circulation, but they do not remain in the water — they react immediately and disappear.

You still need to maintain a low level of free chlorine (or another residual sanitizer) for ongoing protection between circulation cycles—especially against bacteria or pathogens reintroduced by swimmers or the environment. Many AOP systems operate with reduced chlorine levels, combining the oxidation power of AOP with chlorine’s residual protection.

AOP more thoroughly breaks down contaminants, produces clearer, softer-feeling water, reduces chemical byproducts, and lowers chlorine use, making pool water gentler and lowering long-term chemical costs.

AOP extends water clarity, reduces odors, and lessens irritation. The water may feel closer to fresh water, which benefits sensitive people or those who swim frequently.

AOP systems typically require less frequent chemical handling than traditional chlorine or salt-chlorine systems — but they do have maintenance needs that should be adhered to. That includes periodic inspection and cleaning of the AOP reactor (e.g., UV lamp replacement, if applicable; ozone generator check; or other system-specific maintenance), regular water chemistry balance, and monitoring of circulation flow.

Modern hydroxyl-based AOP systems require only minimal maintenance, generally limited to annual or semiannual checks and routine pool chemistry tests, making them attractive to homeowners seeking less upkeep without compromising water quality.

Yes — while AOP is powerful, it’s not a perfect substitute. Because hydroxyl radicals dissipate immediately after they react, AOP does not provide a lasting sanitizer residual on its own. Without a supplemental residual sanitizer (such as chlorine), water quality could decline between circulation cycles, especially with heavy swimmer loads or environmental contamination.

Also, the effectiveness of AOP depends heavily on proper system design, circulation flow, and consistent maintenance. If the reactor is improperly sized, water flow is insufficient, or chemistry is neglected, the benefits of AOP can diminish. And because the technology tends to be more complex than a simple chlorine or salt system, installation and upfront cost may be higher, which homeowners should weigh against long-term benefits.

Yes — many users of AOP systems report substantial reductions in required chlorine levels once the system is installed correctly and maintained. By using hydroxyl radicals to oxidize contaminants and break down chloramines, AOP reduces chlorine demand, allowing you to run pools with lower free chlorine levels than a conventional system would require.

However, AOP doesn’t eliminate the need for chlorine. Even with AOP, a minimal residual sanitizer remains necessary. But by combining AOP with reduced chlorine output, you can often achieve a balance that delivers clean, comfortable water while minimizing chemical exposure and expense, which many owners find a valuable trade-off for the increased water quality and comfort.

AOP works well for residential pools in seasonal regions like Connecticut, maintaining water quality, reducing chemical handling, and improving comfort when paired with suitable circulation equipment.

Because AOP doesn’t require constant manual chemical addition once it’s up and running, it can be especially appealing for seasonal pool owners who want reliable water quality without an ongoing maintenance burden. Combined with regular winterization and spring start-up service, AOP offers a solid balance of performance and convenience for typical Northeastern pool owners.

When selecting an AOP system, you’ll want to consider several key factors: pool volume and circulation capacity, system compatibility with existing plumbing and filter equipment, ease of maintenance, and whether the system uses hydroxyl-based oxidation or a UV/ozone hybrid. A proper fit ensures the AOP reactor treats all pool water efficiently as it circulates.

It’s best to choose models from reliable manufacturers with good support and easy maintenance. The right AOP system should fit smoothly into your pool’s pump and filter, and your pool service provider should confirm that water flow and turnover are optimized for treatment.

Consider AOP in a new build, major upgrade, or if experiencing ongoing water quality problems with standard systems, such as recurring chloramine odors or algae.

For owners with chlorine or salt pools wanting less chemical use and better water quality, AOP is a practical retrofit—if combined with strong circulation and steady upkeep. For new pools or major renovations, installing AOP from the beginning can reduce ongoing maintenance and enhance comfort.