The smell of chlorine in pool water: what it really means

Especially now, at the start of the outdoor swimming season, you sometimes notice that characteristic ‘smell of chlorine’ in swimming pools. This is often mistakenly interpreted as a sign of high chlorine levels and therefore of particularly clean water. In fact, the opposite is true: a strong smell of chlorine indicates poor water quality and is a warning sign of the formation of so-called chloramines (also known as combined chlorine).

Chlorine is added to the pool water to kill bacteria, viruses and algae and to keep the water hygienic. This active chlorine is referred to as free chlorine. However, when free chlorine reacts with organic contaminants introduced into the water by bathers – such as sweat, urine, skin flakes, cosmetics or lotions – chemical compounds known as chloramines are formed. There are various types of chloramines (mono-, di- and trichloramines), with trichloramine being the main cause of the pungent odour.

Chloramines are not only responsible for the unpleasant odour, but also have other adverse effects: They can irritate the eyes, skin and respiratory tract. This often manifests as red eyes, itchy skin and coughing or breathing difficulties, particularly in sensitive individuals or those with asthma. Furthermore, combined chlorine has significantly lower disinfecting power than free chlorine. This means that a pool with high chloramine levels is not optimally disinfected despite the ‘chlorine smell’, and germs can multiply more easily.

To minimise the formation of chloramines and avoid the pool odour, showering beforehand is very important! Please remember this before entering the water in the swimming pool! This way, nothing stands in the way of safe and carefree swimming enjoyment.