After learning about the possibility of contracting illnesses and infections from a trip to the beach, many people ask us whether it is simply “safer” to swim in pools.

While Swim Guide’s expertise lies in untreated recreational water, such marine and freshwater beaches, lakes, rivers, and ponds, we do know that the majority of reported recreational water illnesses are in fact contracted from pools and other treated water.

Not to worry. In order to provide you with the tools you need to stay healthy at the pool we turned to the experts: The Centre for Disease Control (CDC) and their Healthy Swimming program.

The CDC has incredible and fascinating (and at times disgusting) information about treated water quality that everyone should know in order to keep themselves and their fellow bathers healthy in the pool.

Pool water quality FAQ

What is treated water?

Treated water is water that has been treated with chemicals in order to kill microorganisms that can cause illness and infections in humans. Treated waters include indoor and outdoor pools, hot tubs, water parks, and water play areas such as splash pads. Chlorine is the most common and effective chemical used to disinfect water.

Photo by Cristian Stefanescu

How do harmful microorganisms (germs) get into treated water?

Germs are carried into treated recreational water on our bodies. When the CDC says “the pool is literally only as clean as we are” the CDC absolutely and without a doubt means the pool is only as clean as we are.

Our hair, our hands, our feet, our nose and mouth, our skin, and our butts are the biggest germ buses.

What kind of germs are in pools and how can they affect me?

The most common microorganisms found in pools are:
E. coli O157:H7.

These microorganism can cause a variety of Recreational Water illnesses (RWI) such as gastrointestinal, skin, ear, respiratory, eye, neurologic, and wound infections. According to the CDC diarrhea is the most commonly reported RWI.

Now is a good time to think about how water much you swallow in 45 minutes of swimming:

Adults: 1 tablespoon
Kids: 2 ½ tablespoons

How are pools disinfected ?

When it comes to treating water, chlorine and pH are the dynamic duo. They are the first line of defence against the microorganisms that can cause RWIs.

Basically, chlorine works to kill germs and the level of pH determines how well the chlorine does its job.

Chlorine is used to zap the microorganisms. So the amount of chlorine in a pool needs to be monitored constantly because, as the chemical kills germs, the levels drop. Chlorine levels should ideally be kept at between 1.0 – 3.0 ppm.

PH levels need to be monitored closely as well because when the pH level goes up chlorine is no longer effective at killing germs.

So, if a pool has a really Chlorine-y smell that’s a good thing, right?

Nope. That means the chlorine is reacting with a bunch of products (our body creams, sweat, pee, poop, make-up), and forming chloramines. That chlorine smell many of us take to mean “disinfectant” is actually just the useless chemical irritant chloramine.

Chloramines are what make your eyes red, irritate your lungs, and even cause skin irritations. That strong “chlorine” smell also signals that the chlorine that should be busy killing germs has been used up from reactions with our personal care products and other things we should have washed off our bodies before entering the pool.

If water in pools is treated, why do people get sick?

Chlorine is very effective at killing microorganisms. However, it doesn’t work instantly. Depending on the contaminant, it takes anywhere from a few minutes to almost two weeks for chlorine to destroy a microorganism after it enters the pool.

Keep in mind that throughout the day, many people are coming in and out of the water, each introducing new germs. If chlorine levels aren’t maintained or if people aren’t bathing before entering the pool, it is difficult for the chlorine to keep the water disinfected.

It is also important to note that chlorine is effective against most BUT NOT ALL microorganisms that cause illness in swimmers. Some microorganisms such as Cryptosporidium is chlorine-tolerant.

Healthy swimming: It starts with us

Diarrhea : No swimming if you have the runs

There is no wiggle room here. Don’t go swimming if you have diarrhea. That is an absolute rule.

Diarrhea is the leading cause of illness among swimmers.

If you have diarrhea and go swimming you can give diarrhea to others.

The people you can potentially infect with your diarrhea include: babies, toddlers, children, pregnant women, the elderly, people with compromised immune systems, the lifeguards, and the swim team that is preparing for a big meet.

Not cool.

ALWAYS shower before and after swimming

Showering before going into the pool is not a suggestion. IT IS A MUST. Again, the pool is undeniably only as clean as you are.

Many pools now enforce this regulation before allowing bathers into the water.

Always take a full shower with soap before swimming. You should also shower after swimming to wash off any contaminants you may have come in contact with.

We don’t swim in your toilet – Please don’t pee (or poop) in our pool

Don’t pee or poo in the pool. Urine and feces, your body’s biowaste, belong in the toilet.

Don’t drink the water

Over the course of 45 minutes of swimming the average adult will swallow 16 ml (about a tablespoon) of water.Children swallow about 37 ml (2.5 tablespoons) of water. It only takes a sip of contaminated water to make you sick. Do your best not to drink from the pool.

Download this infographic and put it on your fridge


Credit: CDC, Healthy Swimming, Clean it up, Swimmmers

Credit: CDC, Healthy Swimming, Clean it up, Swimmmers

All of the incredible information in this article, including the fun facts and fantastically informative infographic, were provided by the CDC and their Healthy Swimming program. Thank you CDC!

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Swim Guide
is supported by
* The RBC Foundation

