Dirty pool water can make you sick. It describes water with improper chemical maintenance, a high number of swimmers, or visible contamination, which creates an environment where disease-causing germs thrive. Exposure to this contaminated water leads to infections and illnesses collectively known as Recreational Water Illnesses (RWIs). These sicknesses are contracted by swallowing, breathing in mist from, or having contact with inadequately disinfected water.
The Primary Contaminants in Unsanitized Water
Poorly maintained pool water becomes a breeding ground for biological threats introduced primarily by swimmers. These threats fall into three main categories: parasites, bacteria, and viruses. Among the parasites, Cryptosporidium is of particular concern because it is highly resistant to typical chlorine levels and can survive in properly treated water for over seven days. Giardia is also a common parasite found in contaminated pool water.
Bacteria are also a significant source of illness, including Escherichia coli (E. coli) and Pseudomonas aeruginosa. E. coli is an indicator of fecal contamination, while Pseudomonas is commonly associated with skin and ear infections. Viruses such as Norovirus can also be spread through contaminated water, causing gastrointestinal distress.
Non-biological contaminants like sweat, urine, body oils, and cosmetics are introduced into the water by swimmers. These substances react with the chlorine disinfectant, forming chemical compounds called chloramines. This process reduces the amount of available free chlorine needed to kill germs, lowering the water’s ability to sanitize and making it easier for pathogens to survive and spread.
Recognizing Common Recreational Water Illnesses
Exposure to contaminated pool water can result in several distinct types of sickness, with the most commonly reported being gastrointestinal illnesses. These conditions often involve symptoms such as watery diarrhea, stomach cramps, nausea, and vomiting. Parasites like Cryptosporidium and Giardia, along with bacteria like E. coli and Norovirus, are the primary causes of these infections.
Infections affecting the skin are also common, presenting as folliculitis, which is often called “hot tub rash.” This rash is typically caused by the bacteria Pseudomonas aeruginosa and manifests as itchy, red bumps around hair follicles. People may also experience eye and ear infections following exposure to unsanitized water.
“Swimmer’s ear,” or otitis externa, is an infection of the outer ear canal that allows germs to grow when water remains trapped. Conjunctivitis, commonly known as pink eye, can also occur, often caused by bacteria or the irritant effects of poorly balanced pool water chemistry. If symptoms are severe, include bloody diarrhea, or persist for more than a few days, medical attention is warranted.
Essential Steps for Preventing Waterborne Sickness
Preventing recreational water illnesses requires a shared effort between pool operators and swimmers. Swimmer hygiene is a crucial first step, emphasizing the importance of showering before entering the water. Rinsing off for just one minute removes most of the dirt, sweat, and oils that would otherwise react with and deplete the pool’s chlorine.
Swimmers should also avoid getting into the water if they have diarrhea, as even a tiny amount of fecal matter can introduce millions of germs into the pool. Avoiding swallowing pool water is crucial, as ingestion is the main route of transmission for gastrointestinal RWIs. Parents should take children on frequent bathroom breaks and change diapers away from the water’s edge.
You can also perform a basic check of the water quality before swimming. A common misconception is that a strong chemical smell indicates a clean pool; however, that smell often comes from chloramines, signaling that the chlorine has reacted with waste and is no longer fully effective. Visually, the water should be crystal clear, and you should be able to easily see the bottom of the pool.
For individuals with weakened immune systems, pregnant women, and young children, the risk of severe illness from pathogens like Cryptosporidium is higher. Proper pool maintenance, including maintaining chlorine levels (1–3 parts per million) and a pH between 7.2–7.8, is necessary to ensure the disinfectant can work effectively.