Bottled water companies add small amounts of salt and other minerals primarily to improve the taste of water that would otherwise taste flat, and secondarily to support hydration. Most purified bottled water goes through reverse osmosis or distillation, which strips out virtually everything dissolved in the water. The result is pure H₂O that’s safe to drink but tastes noticeably “empty.” Adding a precise mineral blend back in gives the water a clean, familiar flavor.
How Purification Creates the Problem
Tap water naturally contains dissolved minerals picked up from the ground, pipes, and treatment facilities. When bottled water companies run water through reverse osmosis membranes or distillation, they produce soft, mineral-free water. This ultra-pure water is actually mildly corrosive, meaning it can leach materials from pipes and containers, and it has a distinctly flat or slightly bitter taste that most people find unpleasant. To fix both problems, manufacturers add minerals back in during a step called remineralization.
If you check the label on a bottle of Dasani, Aquafina, or similar purified brands, you’ll typically see an ingredient list that includes things like magnesium sulfate, potassium chloride, and salt (sodium chloride). These aren’t contaminants. They’re added deliberately after purification to rebuild a mineral profile that makes the water taste like, well, water.
Why Minerals Change the Taste So Much
Water flavor is surprisingly complex. The overall perception of drinking water is considered more of a flavor experience than a simple taste, because dissolved minerals interact with each other in ways that enhance or suppress different sensations. Sodium and chloride have a stronger impact on taste than calcium, potassium, or sulfate at comparable concentrations. That’s partly why a tiny amount of salt goes a long way in shaping the flavor profile.
Interestingly, research on taste panels shows that people don’t actually prefer high-sodium water. Panelists tend to rate water with high sodium and chloride concentrations lower, while preferring moderate levels of total dissolved solids with relatively higher amounts of calcium, magnesium, bicarbonate, and sulfate. The water people rate highest also tends to have a slightly higher pH. This is why most brands use a blend of several minerals rather than just sodium chloride alone. The goal is a balanced, neutral flavor, not a salty one.
Temperature matters too. Minerals in water are more noticeable at room temperature and harder to detect when the water is cold. So that bottle from your fridge may taste almost the same regardless of mineral content, but at room temperature, the difference between remineralized and pure water becomes obvious.
The Hydration Angle
Salt also plays a functional role in how your body absorbs water. Sodium is essential to water transport in the small intestine. Your gut moves water across its lining by following the movement of dissolved substances, especially sodium. Without any sodium present, water absorption is less efficient. Early research demonstrated that adding glucose and sodium to water could increase absorption rates by as much as fivefold compared to solutions without them.
This is the same principle behind oral rehydration solutions and sports drinks: sodium paired with a small amount of sugar creates optimal conditions for your intestines to pull water into the bloodstream. The trace amounts in bottled water aren’t nearly as concentrated as a sports drink, but they do nudge absorption in a helpful direction compared to completely pure water.
Alkaline Water and pH Adjustment
Some brands market their water as “alkaline,” meaning it has a pH above 7. Minerals like calcium and magnesium are the tools companies use to raise the pH. Adding these mineral salts shifts water from the slightly acidic side (common after reverse osmosis) toward a neutral or mildly alkaline range. Whether alkaline water offers meaningful health benefits beyond basic hydration is a separate question, but the mechanism is straightforward: the same minerals that improve taste also raise the pH.
How Much Sodium Is Actually in There
The sodium content of most bottled water is very low, typically somewhere between 2 and 20 milligrams per liter depending on the brand. For context, a single slice of bread contains around 100 to 200 milligrams of sodium. So even if you drank two liters of bottled water a day, the sodium contribution would be modest for most people.
That said, water can account for up to 10% of a person’s total daily sodium intake. For someone on a medically restricted low-sodium diet (often capped at 1,500 milligrams per day), even small sources add up. Research has noted that dietitians should be aware of the sodium levels in both tap and bottled water for patients on strict restrictions, since not all bottled waters are equally low. If this applies to you, checking the nutrition label or the brand’s water quality report is worth the few seconds it takes.
What the Label Actually Tells You
FDA regulations draw a clear line between types of bottled water. “Purified water” can have minerals added back in after treatment. “Mineral water,” on the other hand, must contain at least 250 parts per million of total dissolved solids from a geologically protected underground source, and no minerals may be added to it. So if you’re drinking a brand labeled “mineral water,” the minerals come from the earth, not from a factory.
For mineral water specifically, FDA labeling rules require a prominent “low mineral content” notice if total dissolved solids fall below 500 parts per million, and a “high mineral content” label if they exceed 1,500 parts per million. Purified water with added minerals doesn’t have to follow these same disclosure rules, though most brands do list the specific minerals added in the ingredients.
The simplest way to know what’s in your water is to flip the bottle around. Brands that start with a purified source will list their added minerals right on the label: magnesium sulfate, potassium chloride, salt. Brands sourced from springs or underground aquifers generally won’t have an ingredient list beyond “spring water,” because the minerals were already there.