How Clean Are Public Swimming Pools?

Going for a swim in your local community pool can make for a great summer outing with friends and family. But how does your body respond to taking a dip?

Public pools are consistently filled with strangers. Because everyone floats around in the same confined water source, it’s logical to wonder just how well all those pool chemicals sanitize the shallows. Germs and bacteria like to linger in water, after all!

So just how clean are swimming pools, and are they unclean enough to reconsider getting your feet wet in the first place?

How Pool Chemicals Work

We all know a pot of water left outside during a warm summer will quickly be populated with mold, algae, insects, and other natural visitors. Not to mention, humans themselves leave behind traces of soap, perfume, dead skin cells, body oils, and hair, all of which can make a pool dirty.

Since swimming in icky pond water isn’t exactly the best idea, pools use a few tricks to preserve themselves against contaminants and stay crystal clear.

In order to gauge just how clean your local pool is, let’s review how pools attempt to stay as sanitized as possible through the use of several chemicals.

Chemicals are absolutely necessary for pools to stave off bacterial colonies searching for a home. Simply cleaning the surface every so often isn’t enough. To that end, pools make use of sanitizing agents.

The most common sanitizer used in public pools is chlorine. Chlorine is a pool oxidizer, meaning it breaches the cell walls of bacteria, viruses, algae, and other organisms and eliminates them from the inside out. It’s quite efficient compared to its low cost. Pool owners like to treat their pools with chlorine via granules or tablets that coordinate with the pool filters to balance the water’s ppm (parts per million) levels.

Chlorine works best at about 3 ppm. Less than that, and the pool won’t be clean enough for safe swimming. More than that, and health hazards start to emerge for swimmers, including asthma and irritation to the eyes and skin.

Many swimmers hold to the common myth that you can smell when there’s too much chlorine in the water, but this is not entirely true. Pure chlorine that hasn’t oxidated anything yet is odor-free. The chlorine smell most people are used to is the result of chlorine that has attacked a pathogen in the pool and oxidized it into an ammonia-based compound called chloramine. So if the pool is a little too smelly, that’s actually an indicator that it needs more chlorine. Not less.

One of the best pool sanitizer alternatives to chlorine is another chemical called bromine. Rather than oxidizing bacteria and other contaminants, bromine severs the chemical bonds of molecules and destroys them by force. The upside is that bromine remains effective much longer than chlorine. But bromine will still break down into residual compounds called bromamines that will quickly reduce the sanitizing effectiveness of the pool, so maintenance is still important. Bromine will also carry small traces of chlorine for an extra boost in its effectiveness.

Some public pools opt for chlorine-free cleaning solutions, such as biguanide, minerals, or even diluted saltwater to control the cleanliness with varying degrees of success. But just how clean do all of these precautions really make your local swimming pool?

Are Swimming Pools Really Clean?

The answer will depend on a lot of factors. For now, let’s assume we’re dealing with a community swimming pool that is shocked by chlorine on a regular basis.

Although chlorine does kill 99.9% of common waterborne pathogens when used correctly, isn’t perfect. In fact, there are plenty of bacteria strains that are resistant to chlorine. One of the biggest offenders is a parasite called Cryptosporidium, which has been known to survive in treated pools for 3 to 10 days and cause severe diarrhea.

Traces of fecal matter in pools can also introduce harmful strains of E. coli into the water, which chlorine is unable to fight back. E. Coli infections can cause stomach cramps, diarrhea, nausea, and vomiting, and its contaminants are usually ingested by accident among swimmers in public pools.

The best way to prevent these issues is to make sure individuals who are sick, have open wounds, or have diarrhea do not enter the pool. Infants and small children should also have diapers checked frequently. Because chlorine does not immediately kill germs (the process can take anywhere from a few seconds to several minutes), it’s important for swimmers to avoid swallowing pool water.

But the truth is, no amount of sanitizing measures will completely clean out a public pool. Most swimming pool attendants do not screen their swimmers, meaning anyone with any sort of health problems could invite unnecessary illnesses into your summer activities.

While the likelihood of contracting a disease from a treated swimming pool is still small, the threats that could be lingering just beneath the surface only bring more emphasis to the saying “swim at your own risk.”

How Can I Stay Clean and Healthy in a Public Pool?

It’s not impossible to control your exposure to pathogens while going for a swim, to a degree.

Making an effort not to swallow any water is a great first step, but there are a couple of other tricks you can employ to boost your chances of staying healthy.

Showering both before and after you swim in a public pool can be a great way to wash off any dirt or leftover chlorine on your skin. This can help to protect both you and other swimmers from illness.

You might also want to perform your own small appraisal of the pool before you or your loved ones take a dip. Check to make sure the pool’s drain isn’t clogged, review the pool’s latest inspection results, and even consider utilizing small test strips to evaluate the chemical balance of the water. If it’s chlorine, remember that 3 ppm is the target.

Finally, use the bathroom before you enter the pool. Accidents happen—even if they’re small, or you aren’t aware of them! Don’t put other swimmers at risk because you couldn’t hold it in.


Most pool chemicals will appropriately sanitize a pool to accommodate the many people who wish to swim. However, it’s unlikely that any pool will be completely clean, so assess the risks, do some homework, and take as many precautions as you can to ensure you and your company can swim safely and happily this summer!