If your pool smells strongly like chlorine, it may seem like a sign that the water is clean and well-sanitized. In reality, the opposite is often true.
That sharp “chlorine smell” is typically not caused by free chlorine itself, but by combined chlorine, also known as chloramines. For commercial and public pool operators, chloramines are one of the most important water quality indicators to monitor because they affect not only swimmer comfort, but also indoor air quality, staff safety, and regulatory compliance.
Understanding what causes that smell—and how to address it effectively—can help protect your facility, reduce health risks, and improve your guests’ experience.
The strong odor most people associate with chlorine is usually caused by chloramines, not properly balanced free chlorine.
Chloramines form when free chlorine reacts with contaminants introduced by swimmers, including:
As chlorine interacts with these nitrogen-containing compounds, it creates combined chlorine (CC). These byproducts are significantly less effective as sanitizers and are responsible for the strong chemical smell many people notice around pools—especially indoors. The more of these contaminants there are in the water, the worse the water and air quality, exposing swimmers to unnecessary risk of irritation and disease.
In other words, a pool that smells like chlorine often needs attention, not more chlorine.
For commercial pool operators and staff, this is one of the clearest early warning signs that water chemistry is out of balance and additional time needs to be spent to get the pool water completely balanced again.
Why Chloramines Are a Bigger Problem in Indoor Pools
Indoor aquatic facilities face a unique challenge: chloramines don’t just stay in the water.
These compounds can volatilize into the air, particularly in warm, humid environments with heavy bather loads. Once airborne, chloramines accumulate near the water’s surface and in the surrounding pool deck area, contributing to poor indoor air quality. When water is turbulent–for example, during swim meets, pool parties, or spring break–chloramines are more actively released into the air.
This is why swimmers and even observers at indoor pools often experience:
For staff members such as lifeguards, instructors, and maintenance teams who spend extended periods in the environment, the risk is even greater.
High chloramine levels have been associated with respiratory issues, including Granulomatous Lung Disease, also referred to as “lifeguard lung.” Lifeguard Lung causes serious symptoms including lung tightness and coughing. In some facilities, elevated chloramine exposure may also contribute to asthma flare-ups or breathing-related incidents.
This makes odor complaints more than a comfort issue; they can be a serious operational and health concern. While proper ventilation is important for indoor facilities, so is maintaining balanced water quality and preventing high chloramine levels.
Combined chlorine should be one of the first readings reviewed daily. Even before you or staff notice odor or receive guest complaints about strong odor.
A noticeable chlorine smell is often the number one indicator that chloramines are present at elevated levels.
As a general best practice, combined chlorine should remain low. While it’s always best to confirm with your local and regional jurisdictions, the CDC’s Model Aquatic Heatlh Code (MAHC) recommends maintaining combined chlorine at below 0.4 ppm, with actions to reduce levels when they exceed 0.4 ppm.
When combined chlorine begins to rise, you or staff may also notice:
Rather than simply adding more sanitizer, which can potentially enhance the problem, the focus should be on breaking down chloramines, reducing your pool’s contaminant load, and maintaining well-balanced water.
Why Shocking the Pool Every Day Isn’t Always Practical
Breakpoint chlorination, often referred to as “shocking,” is a common way to destroy chloramines.
This process involves raising free chlorine levels high enough to oxidize combined chlorine compounds and restore sanitizer effectiveness.
While this can be effective, it is often not a practical long-term strategy for commercial pools, especially facilities with:
Daily shocking can create several challenges, including:
If your facility aims to drive consistent, sustainable business and a positive guest experience, repeatedly relying on manual shock treatments likely won’t align with your operational goals.
One of the biggest drivers of chloramine formation is bather load.
Every swimmer introduces contaminants into the water, increasing chlorine demand and accelerating combined chlorine formation.
Facilities with heavy usage—including schools, municipal pools, fitness centers, and aquatic therapy facilities—often see chloramine issues build over time if supplemental treatment is not in place.
Peak risk environments include:
As usage increases, chlorine alone may struggle to keep up with oxidation demand efficiently. While it’s important to encourage swimmers to shower before entering the pool–and communicate this regularly–at this point, it’s common for operators to begin evaluating secondary treatment systems.
When It’s Time to Consider a Supplemental System
Depending on what type of facility you operate and how high your average bather load is, there comes a point when supplemental treatment becomes the more practical solution.
One of the most effective options is ultraviolet (UV) water treatment.
UV systems are widely used in commercial aquatic facilities because they help break down chloramines continuously as water circulates through the treatment loop.
Unlike repeated manual shocking, UV provides ongoing oxidation support without disrupting pool access.
Key benefits include:
For indoor pools especially, UV can help improve the environment both in the water and in the surrounding air.
Operational Benefits Beyond Water Chemistry
To start, you’re required to effectively address and manage chloramines in order to be compliant with your local and state regulations. But the law exists because low chloramine levels protect and benefit your staff, guests, and facility equipment..
In addition to meeting compliance standards, reducing combined chlorine helps improve:
Persistent odor complaints can also quickly affect guest perception and your pool’s reputation, even when the pool appears visually clean.
Solving the root cause of your facility’s chloramine issues helps reduce recurring complaints and supports a safer environment.
A Smarter Long-Term Approach
For commercial and public facilities, odor from chloramines is a sign to evaluate combined chlorine levels along with trends in swimmer volume, indoor air quality conditions, and your current oxidation strategy.
Rather than relying solely on repeated shocking, we see many facilities benefit from a more sustainable approach that includes supplemental UV treatment and streamlined water quality monitoring using Pool Shark H2O.
This helps reduce manual intervention (and associated costs) while improving consistency.
Pairing Pool Shark H2O with supplemental treatment systems can also help you maintain healthier water and air quality while reducing the day-to-day burden on staff.
But even if a UV system isn’t in the budget, well-balanced pool water does not include combined chlorine. The easiest, most accurate way to keep your pool water balanced and ensure the lowest level of combined chlorine possible is to test for combined chlorine multiple times a day and a digital system like Pool Shark H2O which does the water analysis for you.
Our secure mobile app provides instant water analysis and chemical dosage recommendations for each water test entered. These calculations are highly accurate and greatly reduce the risk of human error, especially when paired with the LaMotte WaterLink Spin Touch. Health department compliant pool logs are generated automatically, eliminating the need for paper logs that are easily damaged, lost, or forged.
It’s a win-win situation. With Pool Shark H2O, you keep your pool, its swimmers, and your reputation safe and keep yourself organized and efficient at the same time.