You know the one; it's tingy and kind of tingles your nose when you catch a whiff of it.

The sweet smell of chlorine.

I'm smiling because that's not a good sign.

It's a sign people have been doing a bit more than just swimming.

Scientists from the University of Alberta calculated that one commercial-sized swimming pool contained almost 20 gallons of urine.

Even though Michael Phelps told the Wall Street Journal, "I think everybody pees in the pool. Chlorine kills it so it's not bad."

Chlorine doesn't exactly work like that.

Peeing in pools is gross and it can make people sick, too.

A healthy pool has little or no chemical smell; if you, if you have a chemical smell in the pool, you probably have what we call "chloramines".

Chloramines are formed when cleaning agents like chlorine mix with organic compounds.

We're talking sweat, dirt, body oils, and, yes, urine—it can irritate the skin, lungs, and eyes.

The more urine, sweat, and other organic materials in a pool, the less efficient chlorine is at killing the real nasty stuff.

Pool disinfectants work by destroying a pathogen's membrane and proteins.

Chlorine is effective against many germs, but not everything is killed instantly.

While it can kill E. coli within a minute, it can take over 7 days for chlorine to penetrate the cell wall of Cryptosporidium.

Our biggest cause of outbreaks is Cryptosporidium, and Cryptosporidium is a parasite that causes prolonged watery diarrhea—we're talking about diarrhea for 2 to 3 weeks in otherwise healthy people.

Left to their own devices, bacteria can start to colonize and grow into something more.

Biofilm can potentially be found on any surface that's been wet.

It's bacteria that's accumulated so much it creates its own protective layer against chlorine and other disinfectants.

Between 2000 and 2014, there were 493 outbreaks reported from treated recreational waters.

Besides not swallowing the water, there are a couple of ways to be safer and make pools less gross.

Knowing if there's enough chlorine in the water is a good first step.

There's free test strips available at healthypools.org.

For pools and other swimming areas and interactive fountains or water playgrounds where you see that water shooting out of the concrete, we recommend at least one part per million or milligram per liter.

If you're sick or have been sick 2 weeks prior, stay away from the pool.

Take a quick shower before swimming and just don't pee in the pool.

Yeah, I l know. It's real simple.