For most people, filtered tap water hits the best balance of safety, mineral content, and cost. It delivers meaningful amounts of calcium and magnesium, meets strict regulatory standards, and avoids the microplastic load that comes with bottled water. But the full answer depends on where you live, what’s in your local supply, and whether you have specific health concerns.
Tap Water and What’s Actually in It
Municipal tap water in North America contains more minerals than many people realize. Water drawn from surface sources like rivers and reservoirs averages about 34 mg/L of calcium and 10 mg/L of magnesium. Groundwater sources run even higher, averaging 52 mg/L of calcium and 20 mg/L of magnesium. These minerals aren’t just harmless extras. They contribute to your daily intake of nutrients that support bone density, muscle function, and heart rhythm.
Public water systems in the U.S. are regulated under the Safe Drinking Water Act, which sets legally enforceable limits on dozens of contaminants. In 2024, the EPA finalized maximum contaminant levels for six types of PFAS, the industrial chemicals sometimes called “forever chemicals.” The limits are tight: 4 parts per trillion for PFOA and PFOS, and 10 parts per trillion for three other compounds. That said, compliance timelines mean not every system meets these standards yet. You can check your local water quality by looking up your utility’s annual Consumer Confidence Report, which is publicly available.
Bottled Water Is Not Necessarily Cleaner
The assumption that bottled water is purer than tap doesn’t hold up well under scrutiny. Many bottled spring waters actually contain fewer minerals than tap water. North American spring waters average just 18 mg/L of calcium and 8 mg/L of magnesium, roughly half or less of what comes out of a typical faucet. The mineral content varies wildly, with some brands delivering almost nothing.
The bigger concern with bottled water is microplastics. Studies measuring particle counts have found stark differences between bottled and tap water. Bottled water stored in PET plastic containers has shown concentrations ranging from around 14 particles per liter up to several thousand, depending on the study and the particle size measured. Recycled PET bottles tend to shed even more plastic fragments. Tap water, by contrast, generally contains far fewer particles, with several studies reporting counts under 1 particle per liter for larger fragments and modestly higher numbers when counting very small particles. Glass-bottled water falls somewhere in between but still carries more particles than most tap water samples.
Mineral Water: A Meaningful Nutrient Source
True mineral water, especially European brands with moderate mineralization, stands apart from regular bottled water. These products average 262 mg/L of calcium and 64 mg/L of magnesium. Drinking a liter and a half daily from one of these sources could supply a significant chunk of your recommended calcium intake, which matters for people who are lactose intolerant or don’t eat dairy. North American mineral waters are less consistent, with averages around 100 mg/L of calcium but a range stretching from 3 to 310 mg/L. Reading the label is essential because the name “mineral water” doesn’t guarantee high mineral content everywhere.
Distilled and Reverse Osmosis Water
Distilled water and water from reverse osmosis (RO) systems have had virtually all minerals stripped out. This creates two problems. First, the water itself contributes nothing to your mineral intake. Second, and less obvious, cooking with demineralized water pulls minerals out of your food. Losses can reach 60% for calcium and magnesium, and even higher for trace elements like copper (66%) and manganese (70%).
Long-term consumption of very low mineral water has been linked to reduced bone mineral density in children, higher rates of dental cavities, and increased excretion of essential electrolytes. One study found that reducing calcium levels in drinking water from 120 mg/L to 33 mg/L was associated with a 46% increase in cavity rates. Low-mineral water also appears to accelerate bone loss by reducing the body’s production of the active form of vitamin D, compounding calcium deficiency over time.
If you use an RO system because your local water has contamination issues, remineralization is worth considering. Adding a mineral cartridge to your system or using mineral drops can restore calcium to around 90 mg/L, which research suggests is enough to provide meaningful dental and bone protection. Some newer RO systems include a remineralization stage built in.
Alkaline Water
Alkaline water, typically marketed at pH 8 to 9.5, has one narrow area of genuine scientific support. Lab research published in the Annals of Otology, Rhinology & Laryngology found that water at pH 8.8 permanently inactivates pepsin, the enzyme responsible for tissue damage in acid reflux. Regular tap and bottled water, which typically fall between pH 6.7 and 7.4, don’t affect pepsin at all. This makes high-pH water a potentially useful addition for people with laryngopharyngeal reflux, the type that causes throat irritation and chronic cough.
Beyond that specific application, the broader health claims around alkaline water lack strong evidence. Your body tightly regulates blood pH regardless of what you drink, and your stomach acid neutralizes alkaline water within minutes of swallowing it. Paying a premium for alkaline water as a general health strategy isn’t supported by current research.
Sparkling Water and Your Teeth
Carbonation makes water slightly acidic. Commercial sparkling waters range from about pH 4.2 to 5.9, and the critical threshold for enamel erosion is pH 5.5. That means some sparkling waters sit right at or below the level where tooth enamel starts to soften. Lab studies have confirmed that carbonated water produces measurably more enamel surface changes than still water. One exception: carbonated water with added calcium ions showed no significant difference from still water in terms of enamel hardness changes.
In practical terms, plain sparkling water is far less erosive than citrus juices, sodas, or flavored sparkling waters with citric acid. If you enjoy it, drinking it with meals rather than sipping throughout the day limits acid exposure to your teeth.
Hydration Differences Are Smaller Than You Think
A clinical trial that developed a “beverage hydration index” found that sparkling water, sports drinks, tea, coffee, cola, and orange juice all produced the same hydration response as still water when measured by urine output over four hours. The only beverages that hydrated significantly better than plain water were milk (both full-fat and skim) and oral rehydration solutions, which retained about 50% more fluid. The extra staying power comes from their combination of protein, fat, or electrolytes, which slow gastric emptying and reduce urine production.
For everyday hydration, the type of water you choose makes no measurable difference. Electrolyte-enhanced waters don’t hydrate you better than regular water under normal circumstances. They become useful during prolonged exercise, heavy sweating, or illness involving vomiting or diarrhea.
The Practical Answer
If your tap water meets safety standards, a simple carbon filter (like a pitcher filter or faucet attachment) removes chlorine taste and reduces common contaminants while preserving beneficial minerals. This gives you clean, good-tasting water without the microplastic exposure of bottled water or the mineral stripping of distilled or RO systems. If you live in an area with known contamination, such as lead from old pipes or elevated PFAS levels, a more aggressive filter like reverse osmosis makes sense, but add a remineralization step to replace what gets removed.
Mineral-rich bottled water is a solid choice if you’re looking to boost calcium and magnesium intake, but check the label for actual numbers rather than trusting the branding. Glass bottles reduce microplastic exposure compared to plastic. For most people in most situations, though, the water that comes out of your kitchen faucet, run through an inexpensive filter, is the best option available.