Distilled water and bottled water are not the same thing. Distilled water is one specific type of bottled water, but most bottled water you see on store shelves is not distilled. The difference comes down to what’s in the water: distilled water has virtually zero minerals or dissolved solids, while most bottled water contains anywhere from 50 to 500 parts per million of minerals and other dissolved substances.
What Makes Distilled Water Different
Distilled water is made by boiling water, capturing the steam, and condensing it back into liquid in a separate container. This process leaves behind essentially everything that was in the original water: minerals, bacteria, heavy metals, fluoride, and other dissolved substances. The result is water in its most stripped-down form, with a total dissolved solids (TDS) reading between 0 and 10 parts per million.
That near-zero mineral content gives distilled water a flat, neutral taste that many people find unappealing compared to other bottled waters. It also makes distilled water slightly acidic. Fresh distilled water has a pH around 6.9, just below neutral. But once exposed to air, it absorbs carbon dioxide and forms a weak carbonic acid solution, dropping the pH to anywhere between 5.5 and 6.9 depending on how long it sits.
The Many Types of Bottled Water
“Bottled water” is a broad category, not a single product. The FDA recognizes several distinct types, each with its own rules about sourcing and composition.
- Spring water comes from an underground formation where water flows naturally to the surface. It retains the minerals it picked up underground and is often described as crisp or slightly sweet in flavor.
- Mineral water must contain at least 250 parts per million of total dissolved solids from a protected underground source. No minerals can be added after the fact.
- Purified water has been processed through distillation, reverse osmosis, or deionization to meet pharmaceutical purity standards. Distilled water is technically a subcategory of purified water, but not all purified water is distilled.
So when you grab a bottle of water at a convenience store, you’re most likely buying spring water or purified water processed through reverse osmosis, not distilled water. The label will tell you which type it is.
How Reverse Osmosis Differs From Distillation
Most purified bottled water is made using reverse osmosis rather than distillation. Reverse osmosis pushes water through a semi-permeable membrane under high pressure, filtering out contaminants and most minerals. Distillation relies on heat, boiling the water and collecting the vapor. Both methods produce very clean water, but distillation is the only process that completely removes microorganisms. Reverse osmosis removes most contaminants but may leave trace amounts that distillation would eliminate.
Some bottled water brands use reverse osmosis and then add minerals back in for taste. Distilled water, by definition, has nothing added back.
Taste and Daily Drinking
If you’ve ever tasted distilled water side by side with spring or mineral water, the difference is obvious. The minerals in spring and mineral water give them a subtle flavor that most people prefer. Distilled water tastes flat and empty by comparison, because there’s literally nothing in it to create flavor.
For everyday drinking, most bottled water provides small amounts of calcium, magnesium, and other minerals that contribute to your daily intake. Distilled water provides none. Drinking distilled water occasionally is perfectly fine, but relying on it as your only water source over a long period may affect your mineral balance. A 2022 review found that long-term consumption of demineralized water can reduce the quality of certain nutrient intake. The World Health Organization has noted that drinking only low-mineral water may increase urine output in ways that shift electrolyte balance, and it may contribute to lower absorption of calcium and magnesium. These effects matter most if your diet is already low in these minerals.
When Distilled Water Is the Better Choice
Distilled water has specific uses where regular bottled water falls short. CPAP machines for sleep apnea are the classic example. The minerals in spring or purified bottled water leave deposits inside the humidifier chamber over time, reducing performance and shortening the machine’s lifespan. Distilled water prevents that buildup entirely. Your stomach acid can neutralize microorganisms in drinking water, but your respiratory tract has no such defense, which is another reason CPAP manufacturers specifically call for distilled water.
The same logic applies to steam irons, car batteries, laboratory equipment, and home autoclaves. Any device that heats water or relies on pure vapor will work better and last longer with distilled water, because there are no minerals to leave crusty white residue behind. Regular bottled water, even purified varieties, typically contains enough dissolved minerals to cause buildup in these situations.
Which One Should You Buy
It depends entirely on what you need it for. For drinking, standard bottled water (spring, mineral, or purified) is the better everyday choice. It tastes better and contributes trace minerals your body uses. For medical devices, appliances, or any situation where mineral-free water matters, distilled water is what you want. They’re sold in the same aisle, but they’re designed for different purposes, and using the wrong one in the wrong context, like putting spring water in a CPAP machine, can cause real problems over time.