EYE AND SKIN IRRITATION: Most pool owners attribute eye and skin irritation only to excessive chlorine in the pool. Although excessive chlorine will cause eye and skin irritation, it is not the single contributing factor.
For more specific information on eye and skin irritation, select from the following topics:
TOO MUCH CHLORINE: Too much chlorine is a definite cause of eye and skin irritation. If your chlorine level is too high (over 5.5 ppm), then cease its addition into the pool until the level drops to within the ideal 2.0 - 3.0 ppm range. If your chlorine level stays constantly high, you can add Sodium Thiosulfate to assist with lowering the chlorine level.
When you shock your pool (with a chlorine-based shock), you are adding megadoses of chlorine. This will raise the chlorine level in your water, which will cause eye and skin irritation. Therefore, stay out of the pool for at least 8 hours after shocking a pool with a chlorine-based shock.
TOO LITTLE CHLORINE: The discussion on Chlorine Demand stated that chlorine must kill all bacteria, living organisms, ammonia, and other contaminates in the water. Well, chlorine is very effective at killing bacteria, living organisms, and other contaminates (which again are dirt, debris and algae spores), but when ammonia is present, chlorine will combine with it, but cannot successfully kill it, and the two combine to form "Chloramines." Chloramines will remain in the water, and will register as chlorine, but are ineffective at sanitizing, disinfecting, or oxidizing. Although Chloramines register as chlorine, they are undesired. Since this chlorine is now virtually useless, you technically have too little chlorine in the pool.
So then, since chloramines are ineffective and undesired forms of chlorine, how are they removed from the water? Easy - by shocking the pool on a consistent and regular basis. Even if you maintain a 2.0 - 3.0 ppm (ideal) chlorine reading at all times by merely adding chlorine tablets or granular chlorine to the pool, the presence of ammonia will lead to Chloramines, preventing the chlorine from being fully effective. You must shock the pool. Remember, when you shock the pool, though, you will have a very high chlorine reading-which can also lead to eye and skin irritation; stay out of the pool for at least 8 hours after adding a chlorine-based shock.
NOTE: A common myth of swimmers is that too much chlorine is the only cause of eye and skin irritation. Although high chlorine is a definite cause, it is not the only reason-it is not even the leading cause. The presence of chloramines, and in effect, too little Free Chlorine, is a primary cause for eye and skin irritation.
POOR WATER CHEMISTRY: Poor overall water chemistry-primarily due to either high or low pH and Alkalinity readings-will cause eye and skin irritation. You must constantly test and adjust your chemicals to make sure that water chemistry is always adequate and in range.