Pool Smells

The Science Behind the Smell of Chlorine in Pools

In Pool Maintenance How To by Platinum Pools

The smell of pool water on a hot summer day can bring back fond memories of carefree swimming.  However, the smell often associated with pools is not the smell of chlorine but chloramines, which can irritate swimmers’ eyes, lungs, and skin when present in high amounts.  In this blog, we’ll look closer at the chemistry behind pool smell, explore how chloramines are formed, and discuss ways pool managers can effectively manage chlorine levels to ensure a safe and enjoyable swimming experience.

The Chemistry of Pool Smells

Adding chlorine disinfectants to pool water releases hypochlorous acid and hypochlorite ions, collectively known as “free available chlorine” (FAC).  These chlorine compounds play a crucial role in destroying waterborne germs and ensuring the safety of swimmers.  However, when FAC reacts with sweat, oils, and urine from swimmers, it forms chloramines responsible for the pool smell.

The pool smell occurs due to the reaction between hypochlorous acid and ammonia (a component found in sweat and urine) that creates chloramines. In this reaction, the chlorine ions replace the hydrogen ions in ammonia, forming monochloramine, dichloramine, and trichloramine. While monochloramine can function as a disinfectant and is added to water intentionally, dichloramine and trichloramine are undesirable and can cause eye and respiratory irritation.

Showering before entering the pool is advisable to remove sweat and oils to prevent the formation of chloramines and alleviate pool smell.

Managing Chlorine Levels

Pool managers face the challenge of maintaining an appropriate level of free available chlorine to destroy germs effectively.  The free available chlorine reduces while forming chloramines, leaving less chlorine available for disinfection.  The amount of chlorine tied up in chloramine compounds, unavailable as free chlorine, is referred to as combined available chlorine (CAC).  It is crucial to keep CAC levels low to ensure optimal disinfection.

The Pool and Hot Tub Alliance recommends that FAC concentrations in pool water remain in the 1.0 to 4.0 parts per million (ppm) range for chlorine to work effectively.  The FAC should always stay above 1 ppm.  Additionally, CAC levels must remain below 0.2 ppm.  Pool managers can regularly measure FAC and total chlorine (TC) levels using test kits to ensure proper chlorine management.

Minimizing Pool Smells

Swimmers often associate a strong chlorine smell with an overabundance of chlorine in the pool.  However, an irritating odor can indicate a lack of sufficient chlorine.  Pool operators can perform shock treatment or superchlorination to address this issue and eliminate chloramines.  It requires adding extra chlorine to the pool to destroy ammonia and organic compounds that react with chlorine to form chloramines.  For effective chloramine destruction, the FAC concentration of the pool water should be around ten times higher than the CAC level.

Ensuring Pool Safety

Properly disinfected pool water is essential for the health and safety of swimmers.  Pool managers are responsible for adjusting the pool water chemistry to reduce the risk of infections.  There are several indicators that swimmers can look out for to determine if a pool is safe for swimming:

Clear and Blue Water

The pool water should appear clear and blue, allowing visibility of the drain or painted stripes on the floor.  Cloudy or colored water may indicate the presence of algae, making it unsafe for swimming.

Slimy Pool Walls

If the pool walls around the waterline feel slimy to the touch, germs are likely present on the surface.  Swimmers should avoid entering pools with dirty walls so they can avoid getting an infection.

Chemical Odor

A strong chemical odor around the pool is a cause for concern.  Swimmers should avoid using pools with a noticeable chemical smell until proper water treatment.

Swimmers must shower before entering the pool, helping maintain a clean pool environment.  It helps remove substances such as sweat and oils that can contribute to the formation of chloramines.  Additionally, it is crucial to encourage young children to take regular bathroom breaks to prevent accidents in the pool.


Understanding the chemistry that causes chlorine smell in pools is crucial to ensure a safe and enjoyable swimming experience. Chloramines, not chlorine itself, cause a distinct pool smell. Pool operators can prevent the formation of excessive chloramines and minimize pool odor by managing chlorine levels. Swimmers can also contribute to maintaining a hygienic environment by showering before entering the pool and following proper hygiene practices. With these measures, pools can be a refreshing haven for swimmers to enjoy during the summer.