My online research has been challenging to separate out the corn starch or corn Derivatives that are obviously in chlorine weather in tap water or pools. There is medical support backing it but I would also like to hear from the wisdom from this sight. Still learning how to ask questions in the correct format. Thank you for your time.
Chlorine itself will not trigger a corn allergy. That's simply because chlorine is a simple molecule and corn is a complex smörgåsbord of complex organic molecules. However, pools do not typically use pure chlorine gas. They use a compound such as troclosene sodium which is a powder that releases chlorine as it dissolves. The manufacturing of such substances may include additives that could cause problems. In particular, they may use cornstarch as an anti-caking agent.
Given that the material your son may be having issues with is not an active ingredient, tracking the problem down may be difficult. Different manufacturers may use different mixtures. It's entirely possible that one supplier might use cornstarch for anti-caking, while another uses sodium silicate. Wikipedia's page on anti-caking additives doesn't even list cornstarch, so its reasonable to believe its rare in such products, but that doesn't mean your local pool's particular vendor doesn't use it. You'd have to do some digging.
It is far less likely that tap water will have similar issues. There's a simple reality that if drinking water caused harm to those with corn allergies, you wouldn't hear it from "hundreds of people," you would hear it from the doctor because it would be documented scientific fact. I would recommend asking your doctor about the feasibility of such a source of corn derivatives. That being said, do note that many bottled water sources are actually municipally sourced, meaning all they're giving you is tap water.
An interesting test (if you're willing to experiment!) would be to use an activated carbon filter such as those in Brita water pitchers instead of bottled water. The activated carbon will remove the chlorine, but will most likely not interact with any corn derivatives in the water. If your son has trouble with that brita water, but not bottled water, that's an indication that you may indeed be right about what's in the water. If your son can drink the brita water just fine, that suggests it might actually be the chlorine that your son is responding to, independent of any corn allergy.
(Obviously use common sense: as a parent, your child isn't a guinea pig. Learn what you can from experiments, but don't subject your child to anything life threatening in the name of science. That'd just be silly!)