Most mineral water is slightly acidic to neutral, with pH values typically falling between 5 and 8 depending on whether it’s still or sparkling and what minerals it contains. Sparkling mineral water is consistently more acidic than still, because dissolved carbon dioxide creates a mild acid in the water. But the full picture is more nuanced than a single pH number suggests.
Still vs. Sparkling: How Much pH Differs
The biggest factor determining whether your mineral water leans acidic or neutral is carbonation. When carbon dioxide dissolves in water, it reacts with water molecules to form carbonic acid, a weak acid that lowers the pH. This is the same basic chemistry behind ocean acidification, just on a much smaller scale in your bottle.
A study in Clinical and Experimental Dental Research measured the pH of the same brands in both still and carbonated versions and found a consistent drop. One brand (Vimeiro) had a still pH of 7.35, essentially neutral, but its sparkling version dropped to 5.03. Another brand (Carvalhelhos) went from 6.73 still to 4.82 carbonated. Across the board, carbonation lowered pH by roughly one to two full points.
Well-known sparkling brands follow this pattern. S.Pellegrino has a measured pH of 4.96, and Perrier comes in at 5.25. Both are mildly acidic, comparable to black coffee or a weak tea. For context, pure water sits at 7.0 (neutral), orange juice around 3.5, and stomach acid near 1.5. Sparkling mineral water is far closer to neutral than to any truly acidic beverage.
Why Some Mineral Waters Are Less Acidic
Not all mineral water is created equal. The mineral content, particularly bicarbonate, acts as a natural buffer against acidity. Bicarbonate is the same compound your body uses in its own blood-buffering system, and when it’s present in water, it partially neutralizes the carbonic acid from carbonation. At a pH above roughly 8.3, nearly all dissolved carbon dioxide exists as bicarbonate rather than free acid. Most mineral waters sit well below that threshold, but those with high bicarbonate concentrations still end up less acidic than sparkling waters without it.
This is why two sparkling mineral waters can have noticeably different pH values despite both being carbonated. A water with over 1,500 mg/L of bicarbonate will taste and measure differently from one with 200 mg/L. The mineral label on the bottle tells you more about acidity than the bubbles alone.
What “Mineral Water” Actually Means
Under U.S. FDA regulations, water can only be labeled “mineral water” if it contains at least 250 parts per million of total dissolved solids and comes from a protected underground source. No minerals can be added after the fact. This distinguishes it from spring water, which may come from underground but has no minimum mineral content, and from tap water that’s been filtered and remineralized artificially. The naturally occurring minerals, including calcium, magnesium, sodium, and bicarbonate, are what give each mineral water its distinct chemistry and pH profile.
Effects on Your Teeth
Tooth enamel begins to dissolve at a pH of about 5.5. That puts some sparkling mineral waters in a gray zone. S.Pellegrino at 4.96 and Perrier at 5.25 both fall below that threshold, meaning they could theoretically contribute to enamel erosion with prolonged, repeated exposure.
In practice, the risk is small. Mineral water contains no sugar, which matters because sugar feeds the bacteria that produce their own enamel-attacking acids. The carbonic acid in sparkling water is also weak and quickly neutralized by saliva. The concern is more relevant if you sip sparkling water continuously throughout the day, keeping your mouth in a mildly acidic state for hours. Drinking it with meals or in a single sitting rather than all-day sipping minimizes any dental impact. Still mineral water, with a pH typically above 5.5, poses essentially no risk to enamel.
Effects on Digestion
If you have acid reflux or heartburn, the acidity of mineral water might seem like a concern. But research suggests certain mineral waters actually help. A study published in the World Journal of Gastrointestinal Pathophysiology found that mineral water rich in bicarbonate (also called hydrogen carbonate) reduced both the frequency and severity of heartburn. The bicarbonate binds to stomach acid in a reaction similar to how antacid tablets work, producing water and carbon dioxide gas as byproducts.
In one trial, patients with confirmed reflux drank 250 mL of calcium- and bicarbonate-rich mineral water and experienced measurable pH increases in both the esophagus and stomach, with improvements that lasted and differed significantly from a control group drinking tap water. Patients also reported feeling subjectively better. So while the water itself may register as mildly acidic on a pH strip, its effect inside the body can actually be alkalizing, depending on its mineral composition.
How Minerals Shape the Taste
The pH and mineral content of your water affect its flavor in subtle but measurable ways. Calcium and magnesium tend to add a slight bitter or sour edge. Research published in the journal Foods found that calcium becomes noticeably unpleasant above about 610 mg/L, while magnesium hits a dislike threshold around 45 to 60 mg/L. Sodium and bicarbonate, by contrast, tend to smooth out the taste. Higher bicarbonate levels reduce perceived sharpness, which is partly why heavily mineralized, bicarbonate-rich sparkling waters can taste “softer” than lightly mineralized ones despite both being carbonated.
If a sparkling mineral water tastes particularly sharp or biting, it likely has high free carbon dioxide and relatively low bicarbonate. If it tastes smooth with a clean mineral finish, the bicarbonate is doing its buffering work in your mouth just as it does on a pH meter.
Effects on Bone Health
There’s a persistent idea that acidic beverages leach calcium from bones. For mineral water, the evidence points in the opposite direction. Studies on bicarbonate-rich alkaline mineral water have found reduced markers of bone breakdown. In one study, young women drinking alkaline bicarbonate-rich water showed lower levels of parathyroid hormone and C-telopeptides, both indicators that bone was being broken down more slowly. A separate study found decreased osteoclast activity (the cells that dissolve bone) in people consuming alkaline water.
Even mildly acidic sparkling mineral water delivers calcium and magnesium directly, which your body can absorb and use. The net effect of drinking mineral water on bone health appears to be neutral to positive, regardless of whether the water itself is slightly acidic or slightly alkaline. The mineral content matters far more than the pH number on the label.