The term "combined chlorine" can be a bit confusing to those not steeped in chemistry. Combined chlorine is a catch-all term for an entire array of chemicals where chlorine has "combined itself" with an organic molecule or a nitrogen containing compound (urea, ammonia, etc, etc). There are literally dozens of water soluble "combined chlorine" compounds and, in reality, the CC test is only sensitive to a few of them. So, one can have plenty of bad "combined chlorine" compounds in their water without ever knowing it. The good news is that for most residential pools in the bright sunshine, those nasty combined chlorine compounds either never form or they are at such a low concentration that they are harmless. As long as the CC's measured by the test kit are low, the water is perfectly safe to swim in. Public health codes dictate that you should not swim in a pool with CC's greater than 400ppb (0.4ppm) but that's overly restrictive in a residential setting. You'd be hard pressed to find any harm in swimming in water with CC's as high as 1ppm. CC's can fluctuate a bit throughout the day and over time but I've never seen more than 0.6ppm in my clean/clear pool water and it's almost always 0-0.2ppm on any given test day.
Sometimes we all stumble in the pool world before getting back on track. Hopefully this season will be easy stuff. But hey, don't forget to update your signature for us. 
