(The Short Answer)
If you’ve heard that Reverse Osmosis (RO) water is alkaline or "high pH," that is actually a common misconception. In reality, RO water is typically slightly acidic.
While pure water is neutral (pH 7.0), the RO filtration process usually brings the pH level down to a range of 5.5 to 6.5.
Why is RO water slightly acidic?
The filtration process is so effective that it creates "hungry" water. Here is what happens:
Mineral Removal: The RO membrane strips away minerals like calcium and magnesium. These minerals usually act as a "buffer" to keep pH levels high.
CO₂ Absorption: Because the water is so pure and lacks minerals, it quickly absorbs carbon dioxide from the air. This reaction creates a very weak carbonic acid, which lowers the pH.
Is it safe to drink?
Yes. The acidity is very mild—much less acidic than common beverages like coffee, orange juice, or soda. Most people cannot taste the difference, though some describe RO water as having a "crisp" or "clean" flavor.
How to make it alkaline
If you prefer high-pH water for the taste or health benefits, you have two easy options:
Remineralization Filter: Many RO systems now include a final stage that adds minerals (like calcite or magnesium) back into the water to raise the pH.
Mineral Drops: You can manually add alkaline drops or a pinch of mineral salts to your water.
Source: ChatGPT