Where does the pool smell come from?

It is customary to perceive the “smell of chlorine”, especially in heated indoor pools, where the lack of ventilation causes the volatile components to remain in the pool, but what exactly does it smell like?

Chlorine is actually hypochlorous acid and its ion, which in the free form⁽¹⁾ (free residual chlorine) has a high capacity to react with organic matter (dirt) to form residual combined chlorine.

Let’s say, for example, that in a swimming pool one of the bathers urinates. The free chlorine in the water will react with the urea in the urine to form combined chlorine. The type of combined chlorine in this specific case will be in the form of chloramines, which, being volatile, and leave the pool water, giving that characteristic odor. Chloramines will also be formed with the urea contained in sweat.

Therefore, if a pool smells of chlorine, it is because the water has been disinfected. If there were no contaminants in the water (e.g., urea from sweat), the odor would be virtually undetectable.

Therefore, to avoid and minimize this odor, showers before swimming in the pool are very showers before swimming in the pool are very effective to avoid and minimize this odor.to eliminate the sweat on the skin.

Current legislation and other standards establish free chlorine residual concentrations between 0.4 and 3 ppm. ^{(2) (3)} and less than 0.6ppm in the case of combined chlorine.

⁽¹⁾ The proportion of free active chlorine depends on the pH. See http://hsconsultinggroup.net/agua-piscina-verde-con-cloro/

⁽²⁾ ppm are parts per million which is equivalent to mg of active agent (chlorine, in this case) per liter of water.

⁽³⁾ Variable parameters according to regional swimming pool decrees for each Autonomous Community in Spain.

HS Consulting Team