Have you ever been to a public pool? Some people spend entire summers at the local town pool, and kids get especially excited when they learn that they get to have a day in the water. Sure, public pools aren't the prettiest, but they can be fun, albeit overcrowded on the weekends. The water is generally warmer than a private pool and there's usually more space to swim laps. Lots of people go to meet up with friends and family and find that the pool is a lot easier than the beach. What isn't great about that?

While it's pretty common knowledge that pool areas aren't always the cleanest (cold puddles in the bathroom anyone?), many people don't realize how dirty the pools themselves can be. The general consensus is that if you can smell chlorine, then it's safe to swim without worrying about bacteria. Even if you think that there might be some bacteria present, you probably put it out of your head and enjoy a day in the water. Unfortunately, while some of the unknown facts about public pools are just terrible to hear, others are actually dangerous.

Here are the top 20 facts about public pools that you probably don't know but that you should learn before your next swim!

20 20. Chlorine Doesn't Kill All Bacteria

Although swimmers typically think that a chlorine treated pool means that there's no bacteria present, this isn't always true. Cryptosporidium (known as Crypto for short) can actually survive for almost 10 days in a perfectly pristine chlorine treated pool! Because many pools aren't perfectly treated, the odds of having this bacteria present only go up from there.

Although other bacteria are rarer to find, just recently one young pre-teen contracted a super-bug Amoeba (that is known to eat the host's brain) swimming in a public pool in Arkansas. Other bacteria might not be as common as Crypto, but you really never know what you'll find if the pool is public and you don't know exactly how it's been treated.

19 19. 1 in 5 Adults Pees In the Pool

Every child knows that peeing in the pool is a great faux-pas, so it's surprising how often it actually happens. In public pools alone, 1 in 5 adults admitted to regularly peeing in the pool! Keep in mind that this study only asked yes/no questions. Many other adults may pee in the pool sometimes or even all of the time and be too embarrassed to fess up.

Unfortunately, pool water can only be cycled through every so often, meaning that you're most likely swimming in a lot of pee. Sure, the pool might be perfectly chlorine treated (which will render the pee harmless), but chlorine can't change the fact that you're swimming in it.

18 18. Many People Don't Shower Before Swimming

Some public pools ask that any swimmers shower before swimming while others don't have any hard-set rule. Regardless of the actual regulations, many people (both adults and children) forgo the shower before swimming. Some say that the showers are unclean while others just don't want to deal with the hassle. Unfortunately, this lack of showering contributes quite a bit to making the pool water dirty.

Almost anything on your body will wash off when you enter the pool, including fecal matter, bits of dead skin, and any other bacteria your body has picked up during the day. The average pool has a good amount of all of these things floating around, which would be greatly reduced if each and every swimmer showered before entering.

17 17. A "Bleach" Smell Doesn't Necessarily Mean There are Enough Chemicals In the Pool

Have you ever gone to a public pool and been overcome by the strong smell of chlorine? You probably felt better, knowing that the pool was completely decontaminated. However, the opposite is actually true. If the pool is perfectly cleaned and correctly maintained, then you shouldn't really smell chlorine at all. When you do smell chemicals, this usually means that the pool contains a lot of unclean elements.

When the chlorine treatments react with Ammonia (which is found in urine, feces, sweat, and other unpleasant things that might be in a pool), the chlorine smell is produced. Next time you head to a public pool, be wary if it smells too strong!

16 16. Water Doesn't Cause Red Eyes: Contaminants Do

Have you ever seen someone get out of the pool with reddened eyes? Most adults will say that either the chlorine or salt water in the pool causes the red eyes, and that you shouldn't open them or should wear goggles. The real truth (according to scientists) isn't that the water causes red-tinged eyes, and the chemicals in the water don't even contribute: it's all due to the contaminants.

The same contaminants that fall off humans when they enter the pool without showering are the ones that will make your eyes irritated. Actually, it doesn't even make that big of a difference if you don't open them underwater. It's pretty easy to get a few drops of water in your eyes, and that's all it takes to have a reaction.

15 15. Adults and Children Are Both to Blame for Dirty Water

It's easy to go to a public pool, see tens to hundreds of small children splashing around, and think that they're the cause of most of the contamination, however scientists are finding that adults contribute just as much to making a swimming pool dirty.

Adults are just as prone to not shower beforehand and pee in the pool. They also have more of a tendency to sweat than children, and will likely have more products on their skin (such as sunscreen or perfumes) that will make the water even more contaminated. Remember that adult-only pools don't always mean cleaner water, and do your part by showering beforehand.

14 14. Swallowing Pool Water Can Make You Sick, but the Chlorine Isn't the Culprit

Recreational Water Illnesses, known as RWIs, can be caused by being around water, breathing it in, and (most of the time) by swallowing water. RWIs are especially common in pool water - for good reason! The amount of contaminants in public pools are significant. Recreational Water Illnesses can produce a variety of symptoms such as respiratory problems, gastrointestinal issues, and most commonly, diarrhea.

Swallowing water can easily make you feel a little ill, but even if it doesn't turn into a full-blown RWI, the culprit usually isn't chlorine. Any of the typical pool contaminants aren't meant to be consumed by humans, and swallowing more than a few can make you ill very quickly.

13 13. Almost 100% of Competitive Swimmers Pee in the Pool

Have you ever jumped into the pool right after practice for competitive swimmers ended? Usually, open swim time at public pools is squeezed in-between swim practices, and it may seem clean to swim right after practice because only competitive swimmers were in it before. Surprisingly, surveys actually report that almost 100% of competitive swimmers routinely pee in the pool.

Similar to how you can't assume that all kids cause pools to be dirty, don't assume that competitive swimmers help keep it clean. If these surveys are accurate, then right after swim practice is the last time you'd want to take a dip.

12 12. Swimmers Ear is Caused by Active Bacteria

You probably know that swimmers ear isn't good, but what exactly causes it? It's just simply bacteria invading your ear canal. With all of the bacteria floating around public pools, there isn't much you can do to stop it from touching your ears. Unfortunately, there really is no way to prevent swimmers ear except to stay completely out of dirty water, which is pretty impossible when swimming, since dirty water is extremely hard to spot.

Try to swim in clean pools as much as possible, but if you do contact swimmers ear, use ear drops right away to prevent any further (and much worse) infections.

11 11. Sunscreen and Hair Products Lessen Chlorine Effectivity

Have you ever heard of blonde-haired people worrying about their hair turning green? The chlorine severely affects blonde hair, but surprisingly, hair products and sunscreen affect the chlorine power just as much. When a lot of external products are added to the pool, chlorine just isn't as effective.

This is problematic for a few reasons. Firstly, chlorine can't combat any dirty bacteria in the water from our bodies or other animals, but this is inversely being caused by lotions and hair products that we consider good. The lesson is to refrain from using hair products when swimming and put sunscreen on as soon as possible to give it time to dry completely.

10 10. Swim Diapers Almost Always Leak

Have you ever seen a small child wearing a swim diaper? You probably thought that it was responsible of the parent to make sure the child was correctly outfitted, but in reality, swim diapers almost always leak. There isn't much science behind them - they aren't very absorbent (because they would just absorb the pool water), so everything simply slides right out of them.

This is a hard one to tackle, because if swim diapers aren't the answer, what is? Your best bet is to try to avoid swimming with a ton of people and therefore minimize the amount of bacteria in the pool in general.

9 9. You Only Have to Swallow a Tiny Bit of Water to Fall Ill

You might think you're safe if you only jump in the pool for a few minutes, but even swallowing a small amount of water can make you ill if the right bacteria is present. In the year 2000 alone, just about 2,000 illnesses were related to swallowing contaminated pool water; 4 of these resulted in the loss of life. However, many more people get sick and just aren't sick enough that they need to go to the hospital and report it.

Just like when you get food poisoning from a few bites, there are no hard and fast rules about how much water you have to swallow to get sick, especially in a public pool.

8 8. More and More People Get Sick From Pools Every Year

In the year 2000 compared to the year 1990, the rate of people who got sick from public pools rose tenfold! Now, somewhere around 1,400 people report getting mild to severe illnesses from pools, and many others probably go unreported. This is a pretty high number considering the amount of chlorine dumped into public pools.

This number serves as a reminder that chlorine doesn't kill everything. Additionally, many public pools aren't well-cared for and often don't receive the proper treatments to combat all of the bacteria present. Be sure to do your research before choosing a pool to spend your summers at!

7 7. Chlorine Shocks Are Rarely Performed

Performing a shock to a pool means that you add enough chlorine to clear up that chlorine smell that tackles contaminants. It should reset your pool and make it smell like nothing, meaning that you now have a healthy pool. Unfortunately, if you've ever smelled a public pool, you'll know that chlorine shocks are rarely performed.

Some public pools need to be shocked almost daily and are only done monthly! While shocks can be a little costly and take some time, they drastically reduce the amount of illnesses, but it's up to the staff to make sure they're actually getting done.

6 6. There's a Ton of Hair In the Pool

You know when you're swimming in a pool and come across a clump of hair? Sometimes it's stuck to the side of the pool, sometimes to the filter, and sometimes just free floating. You might think it just came off someone's head, but that isn't always the case.

Pools are virtually never drained and cleaned (except at the end of the season) so this hair literally has nowhere to go. You could be swimming with someone's hair that fell off months ago. Isn't that fun? Additionally, the pool stuff isn't likely to clean out the hair since it's really hard to see unless you swim directly into it, which (as you may know) is a super terrible feeling.

5 5. There's Also a Ton of Bandaids

For some reason, many people wear bandaids in the pool, even though the bandaids won't do much to prevent chlorine from getting in any cut as they immediately get soaked through. What usually happens is that these bandaids fall off and end up floating around for an indefinite amount of time.

Similar to hair particles, if you see a gross bandaid in a pool, you really don't know how long it has been in there. Lifeguards and pool staff will only clean them if they see them, although some pools are now instituting a no-bandaid policy. These policies are a step forward, but come across as somewhat voluntary since no one is actually checked for bandaids before entering the pool.

4 4. Bird Droppings Can Effect Humans In Pools

Plenty of birds, ducks, and other flying creatures frequent the pool, especially when no one is paying attention. Similar to other contaminants, bird feces can affect the pool in multiple ways. Firstly, they make the chlorine less effective (which, without chlorine shocks, will affect you when you go swimming).

Secondly, these droppings will stay in the pool until it is thoroughly cleaned. You might think it is fun or cute to see a gaggle of birds swimming in your public pool or even hang out near it, but what this really means is that your pool is probably dirtier than you think.

3 3. If Your Skin Burns When You Get In the Water, You Should Make Sure to Shower First

Most people have felt their skin burning when they enter a public pool. What does this mean? Most likely, that you need to shower. If you have any contaminants on your skin (ranging from bacteria to sunscreen), the chlorine will attempt to burn it off to keep the pool clean. This is a clear message that you yourself are contaminating the pool and that a shower is in order.

Unfortunately, most pool showers are only cleaned once a week! The amount of bacteria in the showers is huge as well. Your best bet is to either find a clean pool (with clean showers!) or shower at home right before coming, making sure to scrub a bit.

2 2. An Improper Balance of Chemical Can Damage Your Teeth

This is a more obscure public pool fact, but you can actually get tooth damage from swimming in a pool that doesn't have the properly balanced chemicals. Almost any dentist will tell you that chlorine imbalances are super bad for your teeth, especially if you spend a large amount of time in the pool (competitive swimmers, for example).

Chlorine that is the wrong type or too high in quantity can erode your enamel. Studies have found that this causes teeth to become discolored or stained and can actually cause extreme sensitivity for the rest of your life. Unfortunately it's difficult to keep your mouth closed while swimming, so opt for finding a clean pool with a good chlorine balance.

1 1. Physical Activity Anyone? You Still Sweat In a Pool

When doing a physical activity, most people sweat. For anyone swimming in a pool, this is no different, but you can't tell because you're already wet with pool water. This can cause a lot of problems. Firstly, dehydration is often an issue for swimmers because they don't realize how much they're overexerting themselves.

Secondly, sweat releases a lot of toxins. Usually this is fine (as long as you don't touch other sweaty people while exercising), but in a pool, you end up swimming in all of that sweat. If you're a competitive swimmer, at a workout class, or even in a crowded people on a hot day, you can expect to be right in everyone else's sweaty toxins.

References: CBSNews.com, Mashable.com, Buzzfeed.com, Popsci.com, Cracked.com