What is the difference between purified and distilled water?

December 14, 2025 •

4 min read

According to the U.S. Pharmacopeia, for water to be classified as purified, it must contain no more than 10 parts per million (PPM) of total dissolved solids. While both are treated for cleanliness, the fundamental difference between purified and distilled water lies in their unique processes, varying levels of purity, and mineral content.

Quick Summary

The main distinction lies in their processing methods and final composition. Distilled water is created by boiling and condensing steam, removing almost all impurities and minerals. Purified water undergoes multiple filtration processes, including distillation or reverse osmosis, achieving high purity but potentially retaining some minerals.

Key Points

Purification Method: Distilled water is created through boiling and condensing, while purified water uses multiple processes like reverse osmosis, ion exchange, or carbon filtration.
Purity Level: Distilled water is nearly 100% pure H₂O, with virtually all impurities and minerals removed. Purified water is also highly pure, with a TDS of less than 10 PPM, but may contain trace minerals.
Mineral Content: Distilled water is completely stripped of minerals and electrolytes. Purified water may retain some minerals, which often improves the taste.
Taste Profile: The mineral-free nature of distilled water can result in a flat taste, whereas purified water typically has a crisper, more appealing flavor for drinking.
Best Applications: Distilled water is ideal for medical devices and lab equipment where absolute purity is crucial. Purified water is generally preferred for everyday drinking.
Health Considerations: While both are safe, purified water retains minerals beneficial for health, while exclusive, long-term consumption of distilled water could potentially lead to deficiencies if not supplemented by diet.
Energy Use: Distillation is an energy-intensive process requiring boiling, while other purification methods like reverse osmosis are generally more energy-efficient.

Both purified and distilled water are significantly cleaner than standard tap water, but they are not interchangeable. Their differences arise from the specific purification techniques used, which affect their final composition, taste, and ideal applications. Understanding these distinctions is key to choosing the right type of water for your health, household appliances, or laboratory needs.

The Purification Process: From Tap to Pure

Water can be purified in several ways, and the term "purified water" is a broad category that can include different processes. Distillation is just one of these methods, but it's a specific one with a distinct outcome.

How Purified Water is Made

For water to be legally labeled as "purified," it must have a Total Dissolved Solids (TDS) level of less than 10 parts per million (PPM), regardless of the source. This is achieved through various methods, which can be used individually or in combination. These techniques strip the water of most contaminants, including chemicals, bacteria, viruses, and heavy metals, but may leave some beneficial minerals behind depending on the exact process.

Reverse Osmosis (RO): This process uses a semi-permeable membrane to remove dissolved ions, molecules, and larger particles from drinking water by applying pressure. It is highly effective at removing contaminants but is less energy-intensive than distillation.
Ion Exchange: This method uses special resins to remove mineral ions from water, resulting in deionized water.
Carbon Filtration: Water is passed through activated carbon filters that trap and remove organic compounds, chlorine, and other chemicals that affect taste and odor.

How Distilled Water is Made

Distillation is a specific, single method of purification that produces a high level of purity. The process mimics the earth's natural hydrologic cycle on a smaller scale:

Boiling: Impure water is boiled, turning it into steam. Impurities, such as minerals, salts, and heavy metals, have higher boiling points and are left behind.
Condensing: The steam rises into a separate chamber and is cooled, causing it to condense back into liquid water.
Collection: This newly formed liquid is collected in a sterile container, resulting in water that is nearly 100% pure H₂O, free from almost all contaminants and minerals.

Comparison: Purified Water vs. Distilled Water


Feature	Distilled Water	Purified Water
Purification Method	Involves boiling water into steam and then condensing it back into liquid.	Can use multiple methods like reverse osmosis, deionization, or carbon filtration.
Purity Level	Almost 100% pure; virtually all minerals, salts, and contaminants are removed.	Highly pure, with a TDS of less than 10 PPM. May retain some beneficial minerals depending on the method.
Mineral Content	Essentially mineral-free. The distillation process strips out minerals like calcium and magnesium.	Varies by process, but often retains some beneficial minerals that contribute to taste and health.
Taste	Can have a flat or bland taste due to the lack of dissolved minerals.	Generally has a crisper, more pleasant taste, which many people prefer for drinking.
Best For	Use in small appliances like CPAP machines, humidifiers, and irons to prevent mineral buildup. Also used in laboratories and for certain medical applications.	Everyday drinking water. Often sold in bottled form for consumer hydration.
Energy Consumption	Energy-intensive, as it requires heating water to its boiling point.	Typically more energy-efficient than distillation, especially with methods like reverse osmosis.

Choosing the Right Water for Your Needs

The choice between purified and distilled water depends largely on the intended application. For most everyday drinking purposes, purified water is often the preferred choice due to its better taste and the retention of some beneficial minerals. However, in specific cases where mineral content is a liability, distilled water is the superior option.

When to Use Distilled Water

Medical Equipment: Devices like CPAP machines require distilled water to prevent mineral buildup and ensure proper function.
Lab Work: Laboratories rely on distilled water for experiments and processes where trace minerals could interfere with results.
Small Appliances: Using distilled water in steam irons or humidifiers prevents mineral deposits, prolonging the life of the appliance.

When to Use Purified Water

Drinking: For daily hydration, purified water offers a safe, clean, and often more palatable option than distilled water.
Cooking: It can be used for cooking and preparing beverages where you want a neutral-tasting water that won't interfere with flavors.
Commercial Beverages: The food and beverage industry uses purified water to ensure a consistent, clean base for their products.

Potential Health Considerations

While both are safe for consumption, some health implications are worth noting. A balanced diet provides the necessary minerals, so a lack of minerals from drinking water is typically not a major concern for most healthy individuals. However, long-term consumption of only distilled water could potentially lead to mineral deficiencies if a person's diet is lacking. Conversely, if tap water quality is poor, drinking purified water can be a reliable way to reduce exposure to potential contaminants. For individuals with specific health conditions or weakened immune systems, seeking the advice of a healthcare professional is always the best course of action.

Conclusion

Ultimately, the choice between purified and distilled water hinges on its purpose. Both offer a safer, cleaner alternative to potentially contaminated tap water, but they achieve this via different routes. Distilled water is the gold standard for applications demanding absolute purity, such as scientific experiments and sensitive machinery, as its process removes almost everything, including beneficial minerals. Purified water, on the other hand, is an excellent choice for daily drinking and general consumption, providing clean water while potentially retaining a more pleasant taste. By understanding the distinct processes and end results, consumers can confidently choose the right type of water for their specific needs.

World Health Organization (WHO) - Guidelines for Drinking-water Quality

Frequently Asked Questions

Not necessarily. While distilled water is purer from a chemical standpoint, it lacks essential minerals like calcium and magnesium. For daily drinking, purified water is often considered a better option as it provides hydration and may retain some beneficial minerals.

It is not recommended. Medical devices like CPAP machines and steam irons require distilled water to prevent mineral buildup and scaling. While purified water has a low TDS, it may still contain trace minerals that can damage the equipment over time.

Yes, it does. Distilled water is known for its flat taste because the distillation process removes all dissolved minerals. Purified water, which often uses reverse osmosis or other methods, can retain some minerals, resulting in a more appealing flavor for drinking.

People primarily choose purified water for drinking because it is free of harmful contaminants and has a more pleasant taste than distilled water. The process removes unwanted impurities while often retaining some minerals that enhance its flavor.

Distilled water is used in labs and medical facilities because its near-perfect purity prevents contaminants from interfering with experiments or sensitive equipment. This level of cleanliness is crucial for sterile environments and accurate results.

Whether purified water removes fluoride depends on the specific method used. Methods like reverse osmosis and distillation are effective at removing fluoride, while standard carbon filters typically are not. It's important to check the specific system's capabilities.

Yes, it is possible to make distilled water at home by boiling and condensing water, but it's important to use clean, sterile equipment to avoid reintroducing contaminants. For household uses, this method is generally safe.