Updated: June 7, 2020
There are is a lot of misunderstanding about how chlorine works to kill harmful contaminants in pool water, as well as misconceptions about what type of contaminants chlorine will kill efficiently. Of course, chlorine can only do its job if it’s maintained at proper levels. That’s why it’s important to frequently test chlorine levels to ensure there is enough free chlorine to fight harmful contaminants. The easiest way to check chlorine levels is with test strips.
In this article, we cover 5 things free chlorine will kill in pool water. If you need to brush up on free chlorine, check out our article What is the Free Chlorine, Combined Chlorine, and Total Chlorine?
#1: E. Coli
E. coli is bacteria found in the lower intestines of warm-blooded organisms, including humans. Consumption of E. coli can have adverse health consequences, most commonly food poisoning. E. coli is often the culprit of numerous food recalls every year. The presence of E. coli in swimming pools is indication that fecal matter is present. Most people carry up to several tenths of a gram of fecal matter with them externally, which pool water will often wash out and disperse. That is why it is recommended to shower before swimming.
Thankfully, E. Coli is no match for chlorine. Maintaining free chlorine levels of at least 3.0 ppm will typically eliminate E. coli bacteria in swimming pools within one minute of the E. coli contacting the pool water
Salmonella is another form of bacteria that may often find its way into pools through the fecal matter of swimmers. It is bacteria that most commonly grows on meat products and certain types of fruits and vegetables that is then ingested. Like E. coli, salmonella can transfer from one host to another through water.
Thankfully, chlorine kills salmonella just as efficiently as it kills E. coli. When chlorine is added to a pool, it interacts with the water to form a combination of chemical compounds, including hypochlorous acid, whose neutrally charged cells bond with the negatively charged cells of bacteria like salmonella and E. coli to effectively kill them.
#3: Hepatitis A
Hepatitis A is an acute form of hepatitis, meaning it typically only lasts for a short time. The hepatitis virus causes inflammation of the liver, which can lead to side effects including fatigue, nausea, and vomiting. Whereas hepatitis B and C may only be transmitted from blood to blood, hepatitis A can be transferred through fecal matter, which is why it is of concern in swimming pools.
Unlike the other items on this list, hepatitis is a virus not bacteria. It is still not fully understood how chlorine sanitizes many types of viruses, only that it does. Among those that it sanitizes is hepatitis A. However, unlike the bacteria on this list, chlorine is not nearly as efficient at sanitizing this virus. It can take up to 16 minutes for chlorine to sanitize hepatitis A after first contact with pool water.
#4: Bacteria from Urine
It was once thought that urine was sterile. Perhaps the most influential of people sharing this belief was Patches O’Houlihan, coach of the Average Joe’s Gymnasium Dodgeball Team. However, it has since been discovered that urine is not sterile and does, in fact, contain bacteria.
The bacteria in urine is typically no match for chlorine, though. Sufficiently chlorinated pools should disinfect urine bacteria within a minute or so of first contact. However, although chlorine sanitizes urine, there are other consequences of swimming in pools with urine
Contrary to popular belief, it is typically not too much chlorine that causes the chlorine smell of a swimming pool. Nor is chlorine responsible from a common eye irritation swimmers experience, called red eye. Urine is responsible for both. When free chlorine combines with bacteria, it forms chloramines (commonly called combined chlorine). Chloramines are responsible for the “chlorine” smell, and a special chloramine that forms from urine bacteria is responsible for red eye.
#5: Bacteria from Perspiration
Although you may not feel like it, you sweat quite a bit when you swim, especially in a hot tub. Swimming is exercise, after all. You may recall from your childhood health class that human sweat contains bacteria, which is what causes your sweat to smell.
Like urine, however, the bacteria found in human perspiration is no match for the sanitizing power of chlorine in your swimming pool. In the same way it kills the other things on this list, chlorine does away with perspiration efficiently and effectively.
#6: COVID 19
According to the CDC, there is no evidence that the virus that causes COVID-19 can be spread to people through the water in pools, hot tubs, or water playgrounds.
To ensure safety, it is important to keep your Chlorine levels at their recommended levels!