Something has always mystified me about swimming pool care. Why is it that owners need to keep adding chlorine products to their pools? My understanding of chemistry is that ionic salts don't evaporate with water. So, in my mind I picture water constantly evaporating and leaving the chlorine behind. This would make the pool more concentrated wouldn't it? Isn't this what made oceans salty over the eons? Whats happening to cause the loss of chlorine? Clearly I'm missing something here. Does it have something to do with the constant UV radiation of the sun (like altering the chemicals or something)? IF that is the case, would keeping the chlorinated water our of sunlight make it stay chlorinated indefinitely? Another similar one is this: I work in the foodservice industry. Many times I have been instructed that when making a dilute chlorine solution (using ordinary bleach as a sanitizer) that it is important to not use very hot water. The explanation was that hot water would "ruin" the bleach or "cause it to evaporate". Again, this doesn't fit at all with my knowledge of things. OK, thanks for any help understanding all of this.