For most people, filtered tap water strikes the best balance of safety, mineral content, and cost. It retains beneficial minerals like calcium and magnesium while removing the contaminants that matter most, and it avoids the microplastic load that comes with bottled water. That said, the “best” water depends on where you live, the condition of your pipes, and what you’re trying to optimize for. Here’s what actually matters when choosing.
Tap Water: Safe for Most, Not for All
Municipal tap water in the United States is regulated under the EPA’s National Primary Drinking Water Regulations, which set legal limits for over 90 contaminants. Lead, for instance, has a maximum contaminant level goal of zero, with an action level of 0.010 mg/L. Arsenic is capped at 0.010 mg/L. In 2024, the EPA finalized the first-ever federal limits on PFAS (sometimes called “forever chemicals”), setting maximum levels as low as 0.000004 mg/L for the two most studied types.
These standards mean that most tap water is perfectly safe to drink straight from the faucet. The exceptions tend to be location-specific: older homes with lead service lines or lead solder in plumbing, rural areas near agricultural runoff where nitrate levels can climb, and communities where infrastructure hasn’t kept pace with contamination. You can check your local water quality by looking up your utility’s annual Consumer Confidence Report, which every public water system is required to publish.
One genuine advantage of tap water is that it usually contains naturally occurring minerals. Water picks up calcium and magnesium as it moves through rock and soil, and these minerals contribute to your daily intake in a meaningful way. A large study of over 324,000 people in the UK Biobank found that higher magnesium levels in household water were associated with a small but statistically significant decrease in cardiovascular disease risk. The relationship between calcium in water and heart health followed a U-shaped curve, meaning moderate levels appeared more protective than very low or very high concentrations.
Filtered Water: The Practical Sweet Spot
If tap water is the baseline, filtration is the upgrade. The two most common home options are activated carbon filters and reverse osmosis (RO) systems, and they do very different things.
Carbon filters, including pitcher filters and faucet-mounted models, are effective at reducing chlorine taste, some pesticides, and certain organic compounds. They’re affordable and easy to maintain. However, they don’t remove dissolved minerals, fluoride, or most heavy metals at the concentrations that matter.
Reverse osmosis systems are far more thorough. RO pushes water through a semipermeable membrane that removes 85 to 99% of dissolved solids. Certified RO systems can reduce arsenic, lead, fluoride, chromium, copper, and PFAS to levels at or below permissible safety limits. The tradeoff is that RO strips nearly everything from the water, including the calcium and magnesium you actually want. Some RO systems include a remineralization stage that adds minerals back in. If yours doesn’t, you’re essentially drinking purified water, which brings its own considerations.
For most households, a carbon filter handles taste and chlorine while preserving mineral content. If your water report shows elevated lead, PFAS, or arsenic, an RO system is worth the investment.
Bottled Water: Convenient but Overrated
Bottled water falls into several categories defined by the FDA. Spring water must come from an underground source that flows naturally to the surface, collected either at the spring or through a borehole tapping the same formation. Purified water is tap or groundwater that has been treated by distillation, reverse osmosis, or a similar process. Mineral water must contain at least 250 parts per million of naturally occurring dissolved minerals from its source.
The assumption that bottled water is cleaner than tap doesn’t hold up well. A 2024 study from Columbia University found that a single liter of bottled water contains an average of 240,000 detectable plastic fragments, with individual brands ranging from 110,000 to 370,000 particles per liter. About 90% of those were nanoplastics, tiny enough to potentially cross cell membranes. Tap water also contains microplastics, but at far lower concentrations. The long-term health effects of nanoplastic ingestion are still being studied, but the sheer volume in bottled water is worth considering if you drink it daily.
If you prefer bottled water for taste or convenience, mineral water is the most nutritionally interesting option. Your body absorbs calcium from mineral water as effectively as, or possibly better than, calcium from dairy products. A bottle of mineral-rich water can deliver a meaningful dose of calcium and magnesium with zero calories. Just know that “spring water” on a label doesn’t guarantee high mineral content. Check the label for specific mineral concentrations.
Distilled and Demineralized Water
Distilled water has been boiled into steam and condensed back into liquid, leaving virtually all minerals and contaminants behind. It’s useful for medical devices, steam irons, and lab work. As a primary drinking water, it has real downsides.
The World Health Organization has flagged several concerns about long-term consumption of demineralized water. Without calcium and magnesium, this type of water doesn’t replace the minerals your body loses through sweat and urine. Over time, this can shift electrolyte balance and increase urine output, which compounds the mineral loss. A 2022 review confirmed that long-term consumption of demineralized water may lower overall intake of key nutrients. If you drink distilled water regularly, you’d need to be more intentional about getting those minerals from food.
The flat, slightly “empty” taste of distilled water is a clue to what’s missing. Most people find it less satisfying to drink, which can subtly reduce how much water they consume throughout the day.
Alkaline Water: Limited Evidence
Alkaline water has a pH above 7, typically between 8 and 9.5, achieved either through natural mineral content or through an ionizing process. It’s marketed with claims about bone health, acid reflux relief, and superior hydration.
The Mayo Clinic’s assessment is measured: some studies suggest alkaline water may help slow bone loss, but it’s unclear whether the added calcium in the water is what drives that effect or whether the benefit persists long-term. Similarly, there’s preliminary evidence that alkaline water combined with a plant-based Mediterranean-style diet may ease acid reflux symptoms, but the research isn’t strong enough to draw firm conclusions. There’s no solid evidence that alkaline water hydrates you faster or more effectively than regular water. Your body tightly regulates its blood pH regardless of what you drink.
Alkaline water isn’t harmful for most people. It’s just not the breakthrough its price tag implies.
How Much You Drink Matters More Than the Type
The average healthy adult needs roughly 11.5 cups (2.7 liters) to 15.5 cups (3.7 liters) of total fluid per day, with the higher end applying to men and the lower to women. That total includes water from food, which typically accounts for about 20% of your daily intake. Coffee, tea, and other beverages count toward the total as well.
The practical takeaway: filtered tap water, kept in a glass or stainless steel container, covers the vast majority of what your body needs. It’s mineral-rich, low in contaminants, free of the microplastic burden that comes with plastic bottles, and essentially free. If your local water has known issues, a filter matched to those specific contaminants is a better investment than switching to bottled water. And if you’re drinking distilled or RO-treated water exclusively, pay attention to getting enough calcium and magnesium from the rest of your diet.