Drinking pool water is not recommended because, despite treatment, it contains a mixture of chemical byproducts and biological contaminants that can cause illness. A swimming pool is an environment constantly exposed to both disinfecting agents and organic waste from human bodies. This combination creates health risks that range from mild gastrointestinal discomfort to severe, chlorine-resistant infections.
Chemical Contaminants in Pool Water
The primary chemical risk in pool water does not come from the disinfectant itself but from the compounds it creates. Chlorine is added to pool water to kill germs, but when it reacts with organic matter introduced by swimmers, such as sweat, urine, body oils, and skin cells, it forms a class of compounds called Disinfection Byproducts (DBPs).
A common type of DBP is chloramines, which include trichloramine, and these are responsible for the distinct “chlorine smell” and the irritation of the eyes, skin, and respiratory tract. Ingesting water with elevated levels of these chemical irritants can lead to immediate symptoms like nausea and stomach upset. Other DBPs, such as trihalomethanes, are also formed and can be absorbed through ingestion, inhalation, and skin contact. Consuming large quantities significantly increases the body’s exposure to these compounds, which have been associated with digestive distress and other long-term health concerns.
Biological Hazards in Swimming Pools
Even properly maintained pools can harbor biological hazards, primarily due to pathogens introduced by other swimmers. These pools are contaminated by human sources, which include skin cells, saliva, and, most notably, fecal matter. When an infected person enters the water, they can release microscopic organisms that cause Recreational Water Illnesses (RWIs).
The most severe health risk comes from waterborne parasites that are highly tolerant of chlorine disinfection. Cryptosporidium (Crypto) is a prime example, as its protective outer shell allows it to survive in standard chlorinated water for days. Ingesting even a small amount of water contaminated with Crypto oocysts can lead to cryptosporidiosis. Symptoms of this infection include profuse, watery diarrhea, stomach cramps, and sometimes vomiting, typically appearing about seven days after exposure.
Another persistent parasite is Giardia intestinalis, which also causes diarrheal illness (giardiasis). While less chlorine-resistant than Crypto, Giardia cysts can still survive for up to 45 minutes in properly chlorinated water, which is long enough to spread infection. The incubation period for giardiasis averages seven to ten days after ingestion.
Accidental Swallowing Versus Intentional Drinking
The severity of the risk is directly related to the volume of water ingested. Accidentally swallowing a small sip of pool water is common during swimming and is typically harmless, possibly causing only temporary, mild stomach upset due to low concentrations of chemical irritants like chloramines. The risk escalates sharply with intentional drinking or the accidental gulping of a large volume. Significant intake increases the load of both chemical DBPs and lurking pathogens, raising the probability of illness. Consuming a large amount of highly chlorinated water can also induce immediate symptoms, such as severe nausea, vomiting, or burning in the throat and stomach.
What To Do After Ingesting Pool Water
After swallowing pool water, the first step is to rinse your mouth and drink a glass of clean, potable water to dilute any ingested chemicals. Most minor exposures require no further action, but monitoring for symptoms is prudent, especially given the incubation periods of common waterborne parasites. Since symptoms for infections like cryptosporidiosis can take several days to a week to appear, it is important to watch for signs of gastrointestinal distress during that time.
Seek immediate medical attention if you experience severe or persistent symptoms. Specific warning signs that warrant a doctor’s visit include vomiting that lasts for more than eight hours, diarrhea that continues for more than three days, or any signs of dehydration, such as dark yellow urine or extreme thirst. Consult a healthcare professional if you experience a high fever or notice blood in your stool or vomit, as these symptoms indicate a potentially serious reaction or infection.