The pH of water measures its acidity or alkalinity on a scale from 0 to 14, where 7 is neutral. Values below 7 indicate increasing acidity, while values above 7 signify increasing alkalinity. This scale quantifies the concentration of hydrogen ions in a liquid: a lower pH means more hydrogen ions, making the substance more acidic, and a higher pH means fewer, making it more alkaline. Pure water, without any dissolved substances, naturally has a neutral pH of 7.
Understanding pH and Water
The pH of water is a significant characteristic because it influences chemical reactions, mineral solubility, and the effectiveness of disinfectants. It can also affect water’s taste, its interaction with pipes, and the presence of certain contaminants. While the U.S. Environmental Protection Agency (EPA) does not regulate pH as a primary health concern for public drinking water, it recommends a range of 6.5 to 8.5, considering it an aesthetic quality that can indicate other issues if outside this range.
The pH of Bottled Water
The pH of bottled water is not uniform; it varies significantly depending on its source and processing. Regular bottled water, which often includes purified or drinking water, typically falls around a pH of 6 to 7. Purified waters, such as those treated by distillation or reverse osmosis, tend to be slightly acidic, ranging from pH 5 to 7.
Spring water, sourced from underground formations, typically has a pH range of 6.5 to 8.5, reflecting its mineral content. Mineral water often has a pH between 5.5 and 8.5. Alkaline bottled water is intentionally processed or naturally sourced to have an elevated pH, usually ranging from 8 to 10.
Factors Affecting Bottled Water pH
Several factors contribute to the varying pH levels observed in bottled water. Natural factors include the geological composition of the water source, which dictates the type and amount of dissolved minerals like calcium and magnesium. These minerals act as natural buffers, helping water resist changes in pH.
Processing methods also significantly influence pH. Purification processes like reverse osmosis (RO) and deionization remove nearly all dissolved minerals, including those that buffer pH. This often results in water that is slightly acidic. The absence of these buffering minerals makes the water more susceptible to changes in pH, particularly from dissolved gases.
Dissolved carbon dioxide (CO2) is another common factor. When water is exposed to air, it absorbs CO2, which reacts with water to form carbonic acid, thereby lowering the pH. This can occur during bottling or storage.
Health and Quality Considerations
The pH of bottled water can have implications for taste and, in some instances, dental health. Water with a very low or very high pH can have an unpleasant taste. Acidic water may taste metallic or sour, while very alkaline water might have a somewhat bitter or soda-like taste.
Regarding health, the human body maintains a tightly regulated pH balance in its internal fluids, such as blood, which typically stays within a narrow range of 7.35 to 7.45. The kidneys and lungs play primary roles in this regulation. Therefore, consuming water with varying pH levels does not significantly alter the body’s overall pH.
However, highly acidic bottled water (below pH 5.5) can potentially contribute to dental enamel erosion over prolonged exposure. Tooth enamel can demineralize when exposed to acids with a pH below 5.5. Continuous consumption without allowing saliva to re-mineralize teeth could be a concern. Conversely, alkaline water may help neutralize mouth acidity, potentially benefiting oral health. The U.S. Food and Drug Administration (FDA) regulates bottled water as a food product and does not set specific pH limitations, though it requires bottled water to be safe for consumption.