Most still mineral water has a pH between 6.5 and 8.5, placing it in the neutral to slightly alkaline range. Sparkling mineral water is more acidic, typically falling between pH 5 and 6. The exact number depends on what’s dissolved in the water, where it comes from underground, and whether it’s been carbonated.
Still vs. Sparkling Mineral Water
The biggest factor that shifts mineral water’s pH is carbonation. Still mineral water sits close to neutral (pH 7), and many natural mineral waters land slightly above that due to dissolved minerals like calcium and magnesium. The U.S. EPA’s secondary guideline for drinking water recommends a pH range of 6.5 to 8.5, and most still mineral waters fall comfortably within it.
Sparkling mineral water tells a different story. When carbon dioxide is dissolved in water, it reacts chemically to form carbonic acid, a weak acid that drops the pH to roughly 5 to 6. That’s the same reaction responsible for the sharp, slightly tangy bite you feel when you drink sparkling water. The more heavily carbonated the water, the lower the pH tends to be.
Why pH Varies Between Brands
Mineral water gets its character from the rock it passes through underground. As water moves through limestone or dolomite, it dissolves calcium and magnesium from the bedrock. These minerals enter the water along with bicarbonate, which is the main chemical species that acts as a buffer and pushes pH upward. A mineral water sourced from carbonate-rich rock formations will generally be more alkaline than one drawn from granite or sandite aquifers with fewer dissolved minerals.
The carbon dioxide present naturally in the aquifer also matters. According to WHO guidance on drinking water chemistry, the carbon dioxide, bicarbonate, and carbonate equilibrium system is the primary controller of pH in natural waters. More dissolved CO₂ at the source pushes pH down; less CO₂ allows it to rise. Groundwater systems tend to have more stable and predictable pH values than surface water because they’re confined and less affected by weather, temperature swings, and seasonal changes. That’s one reason a given brand of mineral water maintains a fairly consistent pH from bottle to bottle.
Does Mineral Water pH Affect Your Teeth?
Tooth enamel begins to dissolve when the liquid surrounding it drops below a pH of about 5.2 to 5.5. Still mineral water, with its near-neutral pH, poses no risk. Sparkling mineral water sits right around that threshold, which has raised questions, but the acid in carbonated water is weak and doesn’t linger on teeth the way acidic foods or sugary sodas do. In practice, the erosion risk from plain sparkling mineral water is considered very low compared to soft drinks (which often have a pH of 2.5 to 3.5) or citrus juices.
If you’re concerned, drinking sparkling water with meals rather than sipping it throughout the day limits the time your teeth spend in contact with the slightly acidic liquid.
pH and Digestive Health
Your stomach acid has a pH around 1.5 to 3.5, so any mineral water you drink is dramatically less acidic than what’s already in your stomach. For most people, the pH of mineral water has no meaningful effect on digestion.
The exception involves acid reflux. A lab study published in the Annals of Otology, Rhinology & Laryngology found that water with a pH of 8.8, specifically alkaline water rich in natural bicarbonate, permanently inactivated pepsin, the enzyme responsible for tissue damage in reflux disease. Standard tap and bottled waters (pH 6.7 to 7.4) didn’t have this effect because pepsin remains stable at those levels. Some naturally alkaline mineral waters approach pH 8.8, which is why they’re sometimes discussed as a complement to reflux management. This doesn’t mean alkaline mineral water replaces treatment, but it does explain why pH has become a talking point in that context.
How to Check a Specific Brand
Every bottled mineral water label lists the mineral composition, and many now include the pH value directly. If yours doesn’t, look at the bicarbonate content. Water with high bicarbonate (above 300 mg/L) tends to have a higher, more alkaline pH. Water with low bicarbonate and added carbonation will sit at the acidic end of the spectrum.
You can also test pH at home with inexpensive pH strips available at pharmacies or aquarium supply stores. Drop a strip into a glass and compare the color to the reference chart. This gives you a reading accurate to about half a pH unit, which is precise enough to tell whether your water is acidic, neutral, or alkaline.