Reverse osmosis (RO) water is a highly purified form of water, produced by forcing tap water through a semi-permeable membrane. This process effectively removes impurities, contaminants, and dissolved solids. Understanding its pH level helps consumers make informed decisions about their drinking water.
Understanding pH and Alkalinity
The term pH is a measure of how acidic or alkaline a substance is, based on the concentration of hydrogen ions. The pH scale ranges from 0 to 14, providing a standardized way to classify liquids. A pH of 7 is considered neutral. Solutions with a pH less than 7 are acidic, while those with a pH greater than 7 are alkaline, also known as basic. For example, vinegar and lemon juice are acidic, while laundry detergents are alkaline.
The pH of RO Water
Reverse osmosis water is typically slightly acidic, with pH values generally ranging between 5.0 and 7.0. This slight acidity arises because the RO purification process removes most dissolved solids, including minerals like calcium and magnesium bicarbonates. These minerals naturally contribute to water’s alkalinity and buffering capacity. Without these buffering minerals, the purified water becomes more susceptible to changes in pH.
RO water readily absorbs carbon dioxide (CO2) from the air. When CO2 dissolves, it forms carbonic acid, which lowers the water’s pH and increases its acidity. This absorption can cause the pH of initially neutral RO water to drop to an acidic range, sometimes as low as 5.0. The water’s purity allows it to absorb more CO2, leading to a greater pH decrease.
Is Acidic RO Water Safe to Drink?
Despite its slightly acidic nature, reverse osmosis water is generally considered safe for consumption. The human body effectively regulates blood pH within a stable range, regardless of the water’s pH. The slight acidity of RO water is minimal compared to common beverages like coffee, fruit juices, or carbonated drinks, which have much lower pH levels. The United States Environmental Protection Agency (EPA) considers drinking water with a pH between 6.5 and 8.5 to be safe.
The primary consideration with RO water is its lack of beneficial minerals. While reverse osmosis removes harmful contaminants, it also strips out minerals like calcium, magnesium, and potassium. Most essential minerals are obtained from a balanced diet, not primarily from drinking water. For individuals consuming a healthy diet, water’s mineral content is unlikely to significantly impact overall health.
Adjusting RO Water pH
For those who prefer to adjust RO water’s pH or reintroduce minerals, several solutions are available. A common method involves installing remineralization filters, also known as alkaline filters, as a post-treatment stage in an RO system. These filters contain beneficial minerals like calcium, magnesium, and potassium, which dissolve into the water, increasing its pH and improving its taste. Some cartridges raise the pH to an alkaline state, often above 7.0.
Another option is to add concentrated mineral drops directly to the RO water. These drops supplement the water with trace minerals removed during purification. Follow dosage instructions, as they are highly concentrated. Other methods include adding a pinch of baking soda to increase alkalinity, or blending RO water with mineral-rich tap water.