And don't trust your nose.
"Many people think that when a pool smells of chlorine, that means that it's clean," said Mary Ostrowski, director of the Chlorine Issues at the American Chemistry Council, a trade organization. "But that smell is actually chloramines, a substance that results from a mix of chlorine and bacteria, urine and sweat."
So that strong chemical smell actually signifies that the pool's water is exceptionally dirty and should have its chlorine and pH levels tested and adjusted, Ostrowski told Life's Little Mysteries. A perfectly healthy pool would be odorless, and if chloramines levels have reached a point where they can be smelled, the pool water may act as an irritant to a swimmer's eyes, skin and nose.
Harmful germs such as Giardia, E. coli and cryptosporidium (crypto) parasites can spread in public pools that have insufficient chlorine and too-low pH levels. Symptoms of all three illnesses include diarrhea, weight loss, nausea, vomiting, dehydration and stomach cramps.