Bottled water is not a single, uniform substance, and its quality varies significantly between brands and types. Water quality is classified based on its mineral content, which is determined by both the water’s natural source and the purification treatments it undergoes before bottling. The answer to whether bottled water is soft or hard depends entirely on the specific type being considered.
Defining Hard Water and Soft Water
Water hardness is a measure of the concentration of dissolved divalent metallic ions, primarily calcium and magnesium. These ions are picked up naturally as water travels through the environment, dissolving minerals from surrounding rock and soil.
Scientists measure water hardness using parts per million (PPM) or grains per gallon (GPG). Water containing less than 60 PPM of these dissolved solids is classified as soft.
Water is considered moderately hard between 60 and 120 PPM. Hard water starts at 121 PPM and extends up to 180 PPM, while anything above that is classified as very hard water.
How Bottled Water Sources Influence Mineral Content
A bottle of water’s initial hardness level is set by the geology of its source before any processing occurs. Natural sources like aquifers, springs, and wells contain water that has filtered through rock formations. As the water percolates through porous layers, it dissolves various minerals, which are then carried into the water supply.
Water flowing through areas rich in limestone or gypsum, composed of calcium and magnesium carbonates, naturally becomes harder. Spring water is collected from an underground source and its mineral content reflects the surrounding soil and rock. Artesian water, collected from a confined aquifer, also has a mineral profile linked to the geology of its reservoir.
Mineral water is a specific category defined by regulation, requiring it to contain a certain amount of naturally occurring dissolved solids. To be legally labeled as mineral water, the product must contain at least 250 PPM of total dissolved solids originating from the source itself. These products are typically hard, as the high concentration of calcium and magnesium contributes directly to the hardness measurement.
Treatment Methods That Alter Water Hardness
Bottled water labeled as “purified” or “drinking water” often undergoes extensive treatment that fundamentally alters its original hardness. These processes are designed to remove almost all dissolved solids, making the water definitively soft regardless of its initial source. The primary method used by bottlers to achieve this high level of purity is Reverse Osmosis (RO).
Reverse Osmosis forces water through a semi-permeable membrane, blocking nearly all dissolved minerals, including the calcium and magnesium that cause hardness. An RO system typically removes between 95% and 99% of total dissolved solids. Other methods, such as distillation or deionization, also remove these ions, resulting in water with a very low PPM count.
This purification process results in a product classified as soft water, even if it started as hard municipal or well water. Purified bottled water is consistently soft because the minerals have been removed. This contrasts sharply with spring or mineral waters, which retain their natural mineral content.
Practical Differences Between Hard and Soft Bottled Water
The difference in mineral content translates directly into noticeable differences for the consumer, particularly in taste. Hard water, rich in calcium and magnesium, often has a more distinct, full-bodied, or mineral taste. This flavor profile is often preferred by those accustomed to it or who enjoy the taste of a natural mineral spring.
Conversely, soft water, such as purified bottled water, is generally described as neutral, flat, or clean. The near-total absence of dissolved solids means the water lacks the flavor notes provided by minerals. This neutral taste makes soft water preferred for mixing with other beverages, as it does not interfere with the drink’s flavor.
From a nutritional perspective, hard water contributes minor amounts of beneficial minerals to the diet. Mineral water offers the highest concentration of naturally occurring calcium and magnesium. Soft water, having been stripped of these components, provides hydration without contributing significantly to mineral intake. Most purified bottled waters are soft, while natural mineral waters are almost always hard.