A 6.8 pH level in swimming water is not immediately hazardous for a brief swim, but it falls outside the optimal range for a controlled swimming environment. Since 7.0 is chemically neutral, 6.8 is slightly acidic, which presents challenges for swimmer comfort and the long-term maintenance of the pool system. Maintaining the proper pH is crucial because it directly impacts the effectiveness of the disinfection system and the pool’s ability to stay clean.
The Meaning of a 6.8 pH Level
The pH scale measures the acidity or alkalinity of water, ranging from 0 to 14, with 7.0 being the neutral point. Readings below 7.0 indicate acidity, while readings above 7.0 indicate alkalinity. A reading of 6.8 is therefore slightly acidic, meaning it has a higher concentration of hydrogen ions.
For swimming pools, the ideal pH range is between 7.2 and 7.8, with many professionals targeting 7.4 to 7.6. This range is preferred because it closely matches the natural pH of human eyes and mucous membranes, maximizing comfort. A 6.8 pH is sub-optimal because it is below this accepted range.
Water at 6.8 pH is ten times more acidic than water at 7.8, due to the logarithmic nature of the pH scale. While 6.8 is not dangerously corrosive for the swimmer, it signals that the water chemistry is unbalanced. This condition is often temporary, caused by factors like rainwater, organic contaminants, or the introduction of certain chemicals.
Direct Physical Impact on Swimmers
The most immediate and noticeable effect of swimming in 6.8 pH water is irritation to the eyes and mucous membranes. The pH of human tears averages around 7.5, and when the pool water is significantly lower, the difference in acidity causes stinging and redness. This reaction occurs as the body tries to adjust to the more acidic environment.
A 6.8 pH level can also cause mild irritation to the skin, though this is less pronounced than eye discomfort. While the skin’s natural pH ranges from 4.7 to 5.9, prolonged exposure to acidic pool water can cause dryness or itching. Swimmers with sensitive skin or existing conditions may notice this irritation more acutely.
The discomfort caused by a lower pH is often mistakenly attributed to an excess of chlorine, but the cause is frequently the unbalanced acidity. When the water pH is too low, the body’s natural comfort is compromised.
How 6.8 pH Affects Water Disinfection
The efficiency of chlorine, the most common pool disinfectant, is highly dependent on the water’s pH level. Chlorine is most effective when it is in the form of hypochlorous acid, and its concentration is inversely related to pH. As the pH decreases, chlorine’s effectiveness increases dramatically; for example, at a pH of 7.5, chlorine is approximately 50% effective.
A pH of 6.8 causes chlorine to be highly active, which creates management problems. This high activity means the chlorine is consumed and broken down much more rapidly, leading to a quick drop in the residual sanitizer level. Pool operators must then add chlorine more frequently to maintain the required free chlorine concentration, making the water chemistry difficult to manage consistently.
The increased acidity also presents a risk of corrosion to the physical infrastructure of the pool. Acidic water can begin to etch plaster, deteriorate grout, and corrode metal components such as ladders, heaters, and pump parts. Prolonged exposure to water below 7.2 accelerates this damage. A sustained pH of 6.8 is detrimental to the pool’s equipment and long-term sanitation maintenance.