When shopping for drinking water, you’ve probably noticed several different labels: distilled water, purified water, spring water, filtered water, and more. While these terms may sound similar, they don’t always mean the same thing.
Two of the most commonly confused options are distilled water and purified water. Both undergo treatment processes designed to remove impurities, but there’s an important distinction in how these terms are used.
Distilled water is produced through a specific process called distillation, while purified water is a broader category that can include water treated through various methods.
In fact, distilled water can also qualify as purified water under U.S. Food and Drug Administration (FDA) bottled water labeling standards.
So, what makes distilled water different? How does the purification process affect the final product? And how can you determine which type of water is right for your needs?
Let’s explore the science behind these two types of water and why the treatment method matters.
What Is Purified Water?
Purified water is water that has undergone treatment to reduce impurities and meet specific purity standards.
According to the FDA, bottled water produced through processes such as distillation, reverse osmosis, or deionization may be labeled as purified water when it meets the applicable definition.
This means that purified water describes a category of water rather than one specific treatment method.
The purification process can vary depending on the manufacturer, the original water source, and the desired water quality.
Some common purification methods include:
1. Reverse Osmosis (RO)
Reverse osmosis uses pressure to push water through a semipermeable membrane. The membrane allows water to pass through while rejecting many dissolved substances and other contaminants.
According to the Centers for Disease Control and Prevention (CDC), reverse osmosis systems can remove or reduce a variety of contaminants, including certain metals, salts, and microorganisms.
However, removal capabilities vary by system and contaminant.
2. Deionization
Deionization uses ion-exchange materials to remove electrically charged dissolved substances from water.
These substances include positively and negatively charged ions, such as calcium, magnesium, sodium, and chloride.
While deionization can substantially reduce dissolved ionic content, it does not necessarily remove uncharged organic compounds or microorganisms.
For that reason, deionization may be combined with other treatment technologies.
3. Distillation
Distillation uses evaporation, condensation, and precipitation to separate water from many dissolved substances and contaminants.
Unlike membrane filtration, distillation relies on the physical process of changing water from a liquid into vapor and then returning that vapor to liquid form.
Because distillation is one of the methods used to produce purified water, the two terms are not mutually exclusive.
The key takeaway: Not all purified water is distilled, but distilled water that meets applicable purity standards can be classified as purified water.
Source: FDA, 21 CFR § 165.110 — Bottled Water.
What Is Distilled Water?
Distilled water is water that has undergone the process of distillation.
Rather than simply passing water through a filter or membrane, distillation separates water from many contaminants using heat and condensation.
The process consists of three main stages.
Step 1: Evaporation
Water is heated in a boiling chamber until it begins producing steam.
As water changes from liquid to vapor, many dissolved substances do not evaporate with it.
These include minerals such as calcium and magnesium, as well as many dissolved metals and salts.
Instead, these substances remain concentrated in the boiling chamber.
Step 2: Condensation
The water vapor enters a cooling system, where it releases heat and condenses back into liquid water.
This newly condensed water has been separated from many of the substances present in the original water.
Step 3: Precipitation
The condensed water is collected in a separate container or storage tank.
Depending on the distiller’s design, the water may also pass through an activated carbon post-filter to reduce certain volatile organic compounds (VOCs).
The result is water with substantially reduced concentrations of many dissolved minerals, metals, and other contaminants.
The CDC identifies distillation as an effective treatment method for removing or reducing numerous substances, including arsenic, lead, nitrate, sodium, sulfate, calcium, and magnesium.
Source: CDC, About Home Water Treatment Systems.
Distilled Water vs. Purified Water: Key Differences
Although distilled water and purified water can overlap, comparing them helps illustrate why the treatment process matters.
| Feature | Distilled Water | Purified Water |
|---|---|---|
| Definition | Water produced through distillation | Water meeting applicable purity standards |
| Treatment method | Evaporation, condensation, and precipitation | Distillation, reverse osmosis, deionization, or other suitable methods |
| Mineral content | Very low, if any | Depends on the treatment process and any subsequent mineral addition |
| Contaminant reduction | Removes many dissolved minerals, metals, and other contaminants | Depends on the technology used |
| Microorganisms | Distillation inactivates or separates many microorganisms | Depends on the treatment method |
| Taste | Often described as neutral or less mineral-like | Varies with processing and composition |
| Production | Requires heating and cooling | May involve membranes, resins, heat, or multiple treatment stages |
One important distinction is that purified water should not automatically be assumed to contain more contaminants than distilled water.
A properly designed purification system can produce very high-quality water, regardless of whether it uses distillation, reverse osmosis, or a combination of technologies.
The real difference is understanding how the water was treated and what that particular process is designed to remove.
Does Distilled Water Remove More Contaminants Than Purified Water?
This is one of the most common questions people ask when comparing the two.
Removal of Dissolved Minerals
Distillation is particularly effective at separating water from dissolved minerals such as calcium, magnesium, and sodium.
These minerals are responsible for much of the total dissolved solids (TDS) found in drinking water.
Removing calcium and magnesium can also reduce the mineral scale that develops when hard water is heated or evaporates.
Reduction of Heavy Metals
Distillation can reduce concentrations of metals that may be present in water.
Examples include:
- Lead
- Arsenic
- Cadmium
- Chromium
- Barium
The CDC specifically identifies these substances among the contaminants that distillation can remove.
Microorganisms
The heating process used in distillation inactivates many microorganisms, while the evaporation and condensation process provides additional separation.
The CDC lists bacteria, viruses, and parasites among the microorganisms addressed by distillation.
Volatile Organic Compounds
One potential limitation of distillation involves certain volatile organic compounds.
Depending on the distillation system, some of these VOCs can evaporate along with water and potentially carry over into the collected product.
For this reason, certain distillation systems incorporate activated carbon filtration as an additional treatment stage.
Activated carbon can reduce many VOCs, although its effectiveness depends on the contaminant, filter design, and maintenance.
The bottom line: Distillation is a highly capable water treatment method, but contaminant-specific testing is the best way to evaluate an individual system’s performance.
Sources: CDC, About Home Water Treatment Systems; EPA, WaterSense Guide to Selecting Water Treatment Systems.
Does Distilled Water Taste Different from Purified Water?
Have you ever noticed that water tastes different depending on where you drink it?
That’s because the taste of water can be influenced by its mineral composition, treatment process, storage conditions, and other dissolved substances.
Calcium, magnesium, sodium, and other minerals can contribute to the flavor characteristics of drinking water.
Since distillation removes dissolved minerals, distilled water often has a different taste profile from mineral-containing water.
Some people describe distilled water as crisp or neutral.
Purified water can also have a neutral taste, particularly when it has undergone reverse osmosis or another process that removes some dissolved minerals.
However, some commercially purified waters have minerals added after treatment to create a particular flavor profile.
Ultimately, taste is subjective.
The important distinction is that taste alone cannot reliably determine whether water is free from a particular contaminant.
Many dissolved substances cannot be detected by taste, smell, or appearance.
What About Minerals in Drinking Water?
Another common question is whether removing minerals from water makes a meaningful difference.
Water can naturally contain calcium, magnesium, and other dissolved minerals depending on its source.
Distillation removes most of these dissolved minerals, producing water with very low to no mineral content.
But does that mean distilled water is missing something essential?
Minerals are important nutrients that people obtain from their food and beverages, not primarily from their water.
The contribution of drinking water to mineral intake varies based on the mineral concentration in the water and how much a person consumes. The vast majority of minerals in drinking water are not bioavailable for the body to break down and use. Meaning, the minerals your body needs come primarily from your food. A balanced diet is generally the primary source of many essential minerals.
It’s also important to distinguish between nutritional considerations and water treatment performance.
For consumers interested in low-mineral water, the composition of distilled water may be a useful characteristic to consider.
Is Distilled Water Better for Household Appliances?
One practical advantage of distilled water is its low dissolved mineral content.
If you’ve ever noticed white deposits inside a coffee maker, on a faucet, or around a humidifier, you’ve likely encountered mineral buildup.
Hard water contains dissolved calcium and magnesium, which can form scale when water is heated or evaporates.
Because distilled water contains very little of these minerals, it can help minimize mineral deposits in compatible equipment.
Common applications include:
- Humidifiers: Distilled water can help reduce mineral deposits and mineral particles released by certain humidifier designs.
- Steam irons: Some manufacturers recommend distilled or low-mineral water to minimize scale.
- Steam appliances: Low-mineral water may reduce deposits in compatible equipment.
- Laboratory equipment: Distilled water can be useful where controlled water composition is important, although some laboratory applications require additional purification.
- Other household devices: Distilled water may be appropriate when the manufacturer’s instructions specify it.
Always consult the equipment manufacturer’s recommendations before choosing a water type.
Why Does the Purification Method Matter?
When purchasing water, it’s easy to focus entirely on the label.
But terms like “pure,” “filtered,” and “purified” on a label don’t always explain the entire treatment process.
Understanding how water is processed gives consumers more useful information about what they are purchasing.
For example, a bottle labeled purified water may have undergone reverse osmosis, distillation, or another treatment process.
The finished water may meet applicable purity requirements, but the label alone does not necessarily tell you everything about its mineral composition or the specific contaminants reduced or removed during processing.
Likewise, owning a Pure Water Distiller gives you an opportunity to understand how your drinking water is processed.
With a Pure Water Distiller, the treatment process is based on a straightforward physical principle: evaporation, condensation, and precipitation.
99.9% of dissolved substances remain behind in the boiling chamber, where residue may become visible after repeated use.
That visible residue is all the proof you need to have peace of mind about the purity level of your water.
Leave a Reply