Access to clean drinking water drives many consumers to seek options beyond the tap. Growing awareness of aging infrastructure and potential trace contaminants in public supplies has led to a market for highly processed water products. This raises a common question: is purified water truly a superior choice for long-term consumption? Evaluating this requires examining the processes involved, the resulting purity levels, and the overall physiological impact compared to treated municipal water.
Defining Purified Water and Its Production Methods
Purified water is defined by a high standard of purity, established by the United States Pharmacopeia (USP). This standard requires the water to be nearly free of chemicals, limiting total dissolved solids (TDS) to a maximum of 10 parts per million (PPM). Most municipal tap water, for comparison, contains a much higher level of dissolved solids, often ranging from 50 to over 300 PPM.
Achieving this low TDS level requires aggressive treatment methods beyond simple carbon filtration. One primary technique is Reverse Osmosis (RO), which forces water through a semipermeable membrane with microscopic pores. This process physically blocks dissolved inorganic materials and large molecules, typically achieving a 95% to 99% reduction in contaminants.
Deionization (DI) is another method that uses ion exchange resins. These resins chemically exchange charged ions, such as mineral salts, with hydrogen and hydroxyl ions, removing nearly all charged contaminants. Distillation, an older method, involves boiling the water to create steam, which is then condensed back into liquid, leaving virtually all non-volatile impurities behind.
Bottled water labeled “purified” is sourced from public water systems or groundwater, but must be processed using one or a combination of these intensive methods. This separates it from standard filtered water, which may only remove taste-altering compounds like chlorine, and from spring water, which requires minimal treatment.
The Primary Health Advantages of Purification
The direct benefit of drinking purified water stems from the removal of environmental and industrial contaminants. These processes effectively eliminate heavy metals, such as lead and copper, which can leach from aging plumbing infrastructure. Removing these substances offers protection against long-term toxic accumulation.
Purification also targets trace levels of chemicals present in the source water, including pesticides, volatile organic compounds, and chlorine byproducts. While municipal water meets safety standards, purification provides an extra safeguard against substances that can cause gastrointestinal distress or have uncertain long-term effects. Reverse osmosis and distillation are highly effective at removing microbial contaminants like bacteria, viruses, and parasitic cysts, which is important for individuals with compromised immune systems.
The improved taste and odor of purified water is a noticeable advantage for many consumers. By removing residual chlorine and other organic substances, purification makes the water more palatable, which can encourage higher daily fluid intake.
Addressing the Mineral Content Concern
The processes that achieve high purity lead to the primary objection against purified water: demineralization. Reverse osmosis and distillation strip away beneficial dissolved minerals like calcium and magnesium, resulting in “demineralized” water.
Physiological data suggests that drinking water is not the body’s primary source of essential minerals, as most intake comes from food. However, the World Health Organization (WHO) noted that water with extremely low mineral content may be a concern over extended periods. Low-TDS water can be more aggressive, potentially leaching minerals from the body or from food cooked in it, though the practical impact on a balanced diet is debated.
Because of this concern, the WHO recommends that drinking water contain a minimum of 10 mg/L of magnesium and 20 mg/L of calcium. Some manufacturers use remineralization, adding a controlled amount of beneficial minerals back into the water after purification. This step ensures the finished product retains the purity of the treatment while providing a low, consistent level of desirable minerals and improving taste.
Practical Applications and Alternatives
Purified water is well-suited for specific household and specialized applications where mineral content is detrimental. Using demineralized water in appliances like clothes irons, humidifiers, or car batteries prevents the buildup of scale and mineral deposits, extending the appliance’s lifespan and maintaining efficiency. It is also the water type most often recommended for preparing infant formula, though a physician should always be consulted for specific guidance.
For general daily hydration, the choice depends on the quality of the local municipal supply. If tap water is consistently tested and confirmed to meet all public health safety standards, it remains the most economical and environmentally sustainable choice. Only when there are known, persistent issues with a local water supply, such as old lead pipes or contamination events, does the superior contaminant removal of purified water become a clear choice for drinking. A home water quality test can provide the necessary data to determine if highly purified water is a necessity or simply a preference.