I sold water filters for a living for a year and I had to go to a two day school on water, clorine, filters, sales, etc
We were taught to go to a house, to a prospect, and have a swimming pool clorine test kit, that cost $4.00 then, might be $5 or $6 now. It will do 5 tests.
We would frighten the prospective buyer, show them that the water was too highly clorinated to swim in, much less to drink, and they would buy a water filter.
We also learned that you can run city water over the palm of your hand, and the heat of your hand will "disapate it" or make it evaporate within seconds.
I've been challenged on this fact a few times, but I swear on my honor, it is true.
You can buy a cheap swimming pool test kit and try it.
I advice against letting water sit for over an hour in the open with no lid, you might attract algae. Ther is really no need to do that.