Understanding the Fundamentals: What is Purified Water?
Purified water is a broad category for water that has undergone a process to remove contaminants and impurities. The U.S. Environmental Protection Agency (EPA) regulates drinking water quality, setting limits on over 90 contaminants, and purified water often exceeds these standards. The purification process can involve a combination of methods, depending on the source water and the desired level of purity. For water to be labeled 'purified,' it must contain less than 10 parts per million (PPM) of total dissolved solids (TDS).
Common Purification Methods
Purified water is not produced by a single method but rather a suite of technologies designed to target specific types of contaminants.
- Reverse Osmosis (RO): This process forces water through a semi-permeable membrane under pressure. The membrane blocks contaminants, including dissolved salts and bacteria, allowing only pure water to pass through.
- Deionization (DI): Deionization removes mineral ions, such as cations (sodium, calcium) and anions (chloride, sulfate), using ion-exchange resins. This method is highly effective for producing water with very low conductivity, similar to distilled water.
- Filtration: Water is passed through a series of filters. For example, activated carbon filters are effective at removing chlorine and organic compounds that affect taste and odor.
- Distillation: Although often considered a separate category, distillation is also a method of water purification. For commercial purified water production, it might be used as one of several stages.
The Distillation Process: Creating High Purity Water
Distillation is a specific, single method of water purification that relies on boiling and condensation to separate water from its impurities. The process involves heating water until it turns into steam, leaving almost all solids, minerals, and other contaminants behind. The steam is then captured and cooled, causing it to condense back into liquid distilled water.
This method is highly effective at removing a wide range of contaminants, including minerals, salts, most bacteria, and heavy metals. However, it may not remove volatile organic compounds (VOCs), which have boiling points similar to or lower than water and can vaporize along with the steam.
Uses of Distilled Water
Due to its exceptional purity, distilled water is not typically the first choice for daily drinking. Its flat taste, a result of having all minerals removed, is often considered undesirable for consumption. Instead, it has very specific applications where mineral-free water is essential.
- Appliances: In steam irons and humidifiers, distilled water prevents the build-up of mineral scale that can clog equipment and shorten its life.
- Medical and Laboratory Use: Hospitals and laboratories rely on distilled water for sterilization equipment, such as autoclaves, and in chemical mixing to ensure no interfering minerals are present.
- Automotive: Using distilled water in car batteries and cooling systems prevents mineral deposits that can damage components.
Comparison: Distilled Water vs. Purified Water
To clearly differentiate between these two types, consider the key features in the table below.
| Feature | Distilled Water | Purified Water |
|---|---|---|
| Purification Method | Specific: Boiling and condensation. | Broader: Various processes like RO, deionization, and filtration. |
| Total Dissolved Solids (TDS) | Near zero (often <1 ppm). | Very low (<10 ppm). |
| Mineral Content | Virtually free of all minerals, both good and bad. | Removes most impurities but may retain some beneficial minerals. |
| Taste | Flat, lacking the flavor and minerals found in natural water. | Taste can vary but is generally considered more pleasant than distilled water. |
| Common Use | Lab experiments, CPAP machines, appliances. | Everyday drinking, food and beverage production. |
| Cost | Can be more energy-intensive and costly to produce on a large scale. | Often more accessible and affordable for general consumption. |
Making the Right Choice for Your Needs
When deciding between distilled and purified water, your intended use is the most important factor. For drinking, purified water is generally the preferred option. It effectively removes harmful contaminants while often retaining some healthy minerals, which can also contribute to a better taste. For applications where mineral buildup is a concern, such as in appliances or for sensitive laboratory work, distilled water is the superior choice because of its exceptionally low mineral content.
The Impact of Minerals on Taste and Health
The absence of minerals in distilled water is what gives it a distinctively flat and unpalatable taste to many people. While a balanced diet provides the majority of essential minerals like calcium and magnesium, some research suggests that the minerals present in water can also be a beneficial source. Conversely, the complete removal of minerals in distilled water, while not harmful for short-term consumption, is not recommended for regular, long-term drinking.
How to Verify Water Quality
If you have concerns about your home's tap water and want to understand its quality, you can have it tested. The total dissolved solids (TDS) level can be easily measured with a portable TDS meter. A low TDS reading (<500 ppm) is one indicator of water quality, though it is not a complete analysis of all contaminants. Combining different filtration methods, such as activated carbon filters and reverse osmosis, can address a wider range of potential contaminants.
Conclusion
To answer the question, is distilled water the same thing as purified drinking water?, the answer is no. While both are types of treated water with removed impurities, they are not interchangeable. Purified water refers to water processed by multiple methods (including, but not limited to, distillation) to achieve a high standard of purity for drinking, often retaining trace minerals. Distilled water, created specifically through boiling and condensation, is virtually mineral-free and best suited for industrial, medical, and appliance applications where zero mineral content is critical. For daily hydration, purified water offers a more palatable taste and provides beneficial minerals. For specialized needs, distilled water remains the gold standard for pure, mineral-free liquid.
The Process Behind Purified and Distilled Water
The Production of Purified Water
The process of producing commercially available purified water involves multiple stages to ensure high quality and safety. Initial water sources, such as municipal tap water, are first treated with various filtration methods, including carbon filters to remove chlorine and other compounds affecting taste and odor. This may be followed by reverse osmosis (RO), which uses a semi-permeable membrane to trap dissolved salts and other large molecules. Some producers also use deionization (DI) and ultraviolet (UV) light for further disinfection and removal of trace impurities. The final product is tested to ensure the Total Dissolved Solids (TDS) count is below 10 ppm, guaranteeing high purity.
The Creation of Distilled Water
The distillation process is more straightforward, relying on a phase change to purify water. First, water is heated to its boiling point in a container. The impurities, including minerals and salts, have higher boiling points and are left behind as the water evaporates into steam. The steam then travels into a separate chamber, where it is cooled and condenses back into liquid form. This condensate is the distilled water. While highly effective, this method is energy-intensive and can result in water with a flat taste due to the complete removal of minerals.
The Role of Total Dissolved Solids (TDS)
TDS is a measure of the dissolved inorganic salts and organic matter present in water. It is often used as a benchmark for water purity. Purified water, by definition, has a very low TDS level (<10 ppm), while distilled water has an even lower level, often approaching zero. However, a low TDS reading alone does not guarantee the complete absence of all harmful contaminants, such as volatile organic compounds, which is why multi-stage purification is often preferred for drinking water.
The Debate Over Minerals in Drinking Water
The mineral content in water, such as calcium, magnesium, and potassium, is a point of debate. Proponents of purified water argue that retaining these trace minerals can be beneficial for health and improves the water's taste. In contrast, advocates for distilled water or those who rely on a balanced diet for mineral intake believe the absence of minerals in drinking water is not a concern for healthy individuals. For specific medical applications or individuals with certain health conditions, the consumption of mineral-free water may even be recommended.
Conclusion
In summary, distilled water and purified water are distinct products, each with unique characteristics determined by their production methods. Purified water is a broad classification for water that has undergone various advanced purification processes, resulting in a low level of impurities while often retaining some beneficial minerals. Distilled water, created by the specific process of boiling and condensation, is essentially mineral-free and tasteless. Your choice should depend on the application: for daily drinking, most people prefer purified water, while distilled water is essential for specialized uses where mineral-free water is a necessity. Understanding the difference ensures you choose the right water for your needs, whether for health, taste, or equipment longevity.
