I do apologize for the long read. Just my 2 cents.
So it seems to be a widely accepted view on this forum that prevention of a problem is much cheaper and easier than elimination of a problem. I agree completely. Some might think that spending all the money on chemicals to prevent a problem that might never happen is a waste, but as soon as your water chemistry gets all out of whack, you will wish you had acted differently. So we all know about the relationship between TC, FC, and CC. If you maintain proper levels of FC, your CC should hover around zero. This is the prevention method. If you fail to maintain FC, your CC will rise. This is the elimination method. Here's a little something about water treatment not everyone knows. CC is essentially free chlorine (still active) that has been consumed from doing it's job, mainly by it's contact with organic matter. When this process happens, there is a bi-product of the reaction called trihalomethanes (THM). These are very dangerous compounds. The most common THM that occurs in swimming pools that are sanitized with chlorine (doesn't matter which form) is chloroform. THM levels are very closely monitored in drinking water by our municipal water treatment facilities and for very good reason. Now don't get me wrong, there is a huge difference between consumption of the water and swimming in it, yes. But think of how many kids in particular end up with water in their mouths when swimming. Also, most of these compounds are very "volatile" and will rise to the surface of the water and evaporate relatively quickly, which can allow for inhalation during swimming activities. Another factor is absorption through the skin, which has been proven to have an affect on our bodies. I'm not trying to scare anyone out of using their pool. Even the most dangerous activities can be perfectly safe if proper safeguards are taken. Such as how handling a high voltage electrical circuit is completely safe to handle if de-energized. If you maintain proper FC levels then you will minimize THM levels in your water. Simple. Another safety concern with water that is just sitting there in the sun with all sorts of stuff blowing into it all day and isn't properly sanitized is waterborne illnesses. The most common that will develop in water that is not properly sanitized is giardia and cryptosporidium. Neither are likely to kill a person, but the effects on your body will not be pleasant. Basically my point to new pool owners or people that don't put forth much effort in maintaining their pool is this: just stay on top of your water chemistry and you will be rewarded with a worry-free and safe swimming environment.