The growing variety of bottled water options often leads to confusion between distinct products like distilled water and those labeled as “alkaline.” While both are highly purified, their fundamental characteristics and creation processes differ significantly. Distilled water is defined by its extreme lack of dissolved solids, prioritizing purity. Conversely, alkaline water is defined by its elevated pH level, achieved by retaining or adding specific mineral content. This article clarifies how these two types of water are chemically different and why they serve separate purposes.
The Process and Purity of Distilled Water
Distilled water is the product of a purification process designed to remove virtually everything except the hydrogen and oxygen molecules that make up pure water. The method involves heating water to its boiling point, converting it into steam and leaving behind non-volatile substances like minerals, salts, and heavy metals. The collected steam is then cooled and condensed back into liquid form, yielding water with a total dissolved solids (TDS) count near zero.
Although chemically pure water has a neutral pH of 7.0, distilled water exposed to the atmosphere rapidly absorbs carbon dioxide (CO2). This absorption forms a weak solution of carbonic acid (H2CO3), which typically lowers the water’s pH to a slightly acidic range, often between 5.5 and 5.8. Because all dissolved minerals that could act as pH buffers have been removed, the water’s acidity is easily altered by air exposure.
The Chemistry of Alkalinity
Alkalinity in water is a measure of its capacity to neutralize acids, quantified using the pH scale that ranges from 0 to 14. A pH of 7.0 is neutral, while any value above 7.0 is alkaline, or basic. Alkaline water generally has a pH level between 8.0 and 9.5, significantly higher than neutral water.
This higher pH is naturally achieved through the presence of dissolved alkaline mineral compounds, such as calcium, magnesium, and bicarbonates. These minerals act as natural buffers, helping the water maintain a stable alkaline state even when trace amounts of acid are introduced. Water becomes naturally alkaline by flowing over rocks and mineral deposits underground, which infuse it with these buffering agents.
Distilled Water and Alkalinity A Chemical Contradiction
The definition of distilled water creates a chemical contradiction with the concept of natural alkalinity. Distillation fundamentally strips the water of its dissolved solids, including the calcium and magnesium ions necessary for a stable alkaline pH. Therefore, truly pure, un-manipulated distilled water cannot be alkaline; it will be neutral or slightly acidic.
Any commercially available product labeled as “distilled alkaline water” is a two-step product created through post-distillation manipulation. The water is first distilled to achieve high purity and contaminant removal. It is then intentionally remineralized or “enhanced” with alkaline additives like food-grade potassium, magnesium, or calcium compounds to raise the pH. This process combines the purity benefits of distillation with the basicity of added minerals.
Choosing the Right Water for the Right Purpose
The decision between distilled water and alkaline water depends entirely on the intended application, as their unique properties suit them for different uses. Distilled water’s defining feature is its lack of dissolved solids, making it the preferred choice for industrial, laboratory, and medical equipment. It is necessary to prevent mineral buildup and scaling that can damage mechanisms in devices such as:
- Humidifiers
- Steam irons
- Car batteries
- Continuous Positive Airway Pressure (CPAP) machines
Alkaline water, conversely, is primarily chosen for human consumption based on perceived hydration or health benefits. Consumers select it for its higher pH, which is sometimes promoted for its potential to neutralize body acidity or aid in conditions like acid reflux. While scientific evidence supporting these broad health claims remains limited, the added minerals like calcium and magnesium are beneficial nutrients. Distilled water is safe for consumption but is rarely chosen for long-term drinking because of its lack of taste and absence of these dietary minerals.