How Acidic Is Reverse Osmosis Water? October 4, 2022 08:29

Reverse osmosis water is acidic and will typically have a pH in the range of 5.8 - 6.5. Reverse osmosis water is exceptionally pure and pure water is very "hungry" - it seeks to dissolve things.  As soon as reverse osmosis water is exposed to air it begins to absorb carbon dioxide. When carbon dioxide mixes with water it creates a weak acid called Carbonic Acid. Normally a weak acid doesn't affect the pH of a solution because there are many other competing dissolved substances that affect the chemistry. But when even a very small amount of a weak acid is present in almost pure water, the effect on pH can be quite dramatic as we see with RO water. An interesting note about the pH of very high purity solutions is that they are quite unstable. So, even though reverse osmosis water has a relatively low (acidic) pH, as soon as this water encounters another substance - such as your mouth - it will almost immediately take on the pH of that substance. You can read our article about pH, alkalinity and RO water if you'd like to learn more about this topic.

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