If you have reviewed a water quality report or noticed an unfamiliar taste in your drinking water, you may have encountered calcium chloride (\(text{CaCl}_2\)). This salt is a common substance found in both natural environments and municipal water systems. Its presence is usually a deliberate measure to improve water quality, though it can also be introduced through natural geological processes. Understanding why calcium chloride is in your water involves examining its unique chemistry and its specific roles in modern water treatment.
What Exactly is Calcium Chloride?
Calcium chloride (\(text{CaCl}_2\)) is an inorganic salt composed of one calcium ion bonded to two chloride ions. It typically appears as a white, crystalline solid and is highly soluble in water, readily dissolving to release calcium (\(text{Ca}^{2+}\)) and chloride (\(text{Cl}^{-}\)) ions into the solution. This high solubility is a significant factor in how it behaves in your household plumbing compared to other common minerals.
Calcium chloride is distinct from calcium carbonate (\(text{CaCO}_3\)), the main component of traditional “hard water” scale. While both contain calcium, calcium carbonate is largely insoluble and precipitates to form solid deposits. Calcium chloride, in contrast, remains fully dissolved in the water. This means it does not contribute to the hard, crusty buildup typically seen inside kettles and pipes.
How It Enters Water Naturally
Calcium chloride occurs naturally in certain geological formations and is released into groundwater through slow dissolution processes. It is often found in underground brine deposits and in evaporite minerals, which are remnants of ancient dried-up seas. As groundwater filters through these rock layers, it picks up the dissolved \(text{CaCl}_2\), contributing to the water’s natural mineral profile.
The presence of \(text{CaCl}_2\) can also result from unintentional human activities, particularly in colder climates. Calcium chloride is widely used as a de-icing agent on roads and for dust control on unpaved surfaces. Runoff from these applications carries the dissolved salt into surface water sources and groundwater supplies. This environmental introduction acts as a non-point source of chloride contamination, contributing to the total chloride load in many municipal water systems.
Why It Is Intentionally Added to Water
Water utilities and beverage companies intentionally add calcium chloride for several specific purposes, making it a valuable additive in modern water chemistry management. One primary use is for the remineralization of highly purified water, such as water treated by reverse osmosis or distillation. These processes strip away nearly all dissolved solids, leaving the water tasting “flat.” Adding a small, controlled amount of \(text{CaCl}_2\) reintroduces beneficial minerals, improving the flavor profile and providing a more palatable taste.
The compound is also an effective tool for corrosion control within water distribution systems. Soft water, which lacks dissolved mineral ions, can be corrosive to metal pipes, causing leaching of materials like lead and copper. By adding calcium ions, water treatment facilities can increase the water’s hardness, which helps to form a thin, protective layer inside the pipes, reducing the corrosivity of the water and extending the lifespan of the infrastructure.
Calcium chloride is also utilized in the food and beverage industry. In brewing, it adjusts the water’s mineral content, influencing the final beer’s flavor and yeast function during fermentation. It is also added to certain foods, such as canned vegetables and pickles, where it acts as a firming agent to maintain texture and crispness.
Regulatory Standards and Health Considerations
The presence of calcium chloride in drinking water is generally considered safe, and the compound is recognized as safe for food use by regulatory bodies. Calcium is an essential dietary mineral, and chloride is a common electrolyte necessary for bodily functions. At the typical concentrations found in treated drinking water, \(text{CaCl}_2\) poses no health risk.
Regulation focuses primarily on the concentration of the chloride ion. The U.S. Environmental Protection Agency (EPA) has established a Secondary Maximum Contaminant Level (SMCL) for chloride at 250 milligrams per liter (mg/L). This standard is not based on direct human toxicity but rather on aesthetic and technical concerns. Exceeding the 250 mg/L level can lead to a noticeably salty taste and may increase the corrosivity of the water.
The Physical Impact on Your Household Water
The most noticeable effect of elevated calcium chloride levels is the taste of the water. Chloride ions impart a salty or sometimes slightly brackish flavor, which becomes more pronounced as the concentration increases. At very high concentrations, the calcium component can also contribute a faint bitter sensation.
The chloride ion itself can increase the water’s corrosivity. Chloride makes the water more electrically conductive, which promotes the electrochemical reactions that cause metal corrosion in plumbing systems. Because calcium chloride is highly soluble, it remains completely dissolved and contributes to the total dissolved solids (TDS) measurement of the water.