Many people have asked me what causes red eye after swimming in the pool. Most people I’ve talked to on this issue generally suggest that it’s the chlorine in the pool that’s causing this problem. Although this is partially true, chlorine is not usually the main cause of this common swimming problem.
To understand how chlorine works in your pool water, it’s important to know the difference between free chlorine and combined chlorine. Free chlorine’s main job is to disinfect and sterilize pool water to prevent algae growth and keep it free of living organisms that can cause disease. Combined chlorine is chlorine that has combined with other elements or compounds in the pool, such as oils, suntan lotions, organic material, or other chemicals that have been introduced from a variety of different sources. Combined chlorine is not good for sanitizing or disinfecting the pool, but it is good for creating a strong chlorine odor, drying skin, and creating red eyes after swimming.
Another factor that can cause red eyes is the pH of your pool water. The human tear normally ranges between 7.4 and 7.6. Swimming in water in this pH range is ideal. When pool water falls outside of this range, especially if it drops below 7.4, this would indicate that the water is acidic and capable of irritating the eyes, also causing redness.
Sometimes the source of red-eye can be from Total Dissolved Solids (TDS). It can be challenging to determine whether or not this is the problem, because without the proper equipment, it can be difficult to perform a TDS test. To understand what TDS are, if you think that all the water in your pool evaporates, what would remain would be a residue of compounds, elements and particles that have not been captured by the filtration system. Generally, the older the pool, the higher the TDS, as more elements are introduced to the pool over time, increasing the number of TDS.
Regular pool care and constant monitoring of your pool water will let you know what adjustments need to be made to your pool water. It is always better to make smaller adjustments by adding just a little chemical at a time than to make major adjustments that can create wild changes in pool water chemistry. This will ensure that the pool water stays within the recommended ranges and will help prevent red eye from occurring.