Water quality is often described using terms like pH and alkalinity. The pH scale, ranging from 0 to 14, measures how acidic or basic water is, with 7 being neutral. Values below 7 indicate acidity, while values above 7 indicate alkalinity. Alkalinity describes water’s capacity to neutralize acids, often due to the presence of substances like bicarbonates and carbonates. This buffering capacity helps maintain a stable pH. A common question arises regarding copper’s influence on these properties: Does copper make water alkaline?
Copper’s Interaction with Water
Copper does not typically make water alkaline. When water comes into contact with copper pipes or vessels, a process known as corrosion occurs, leading to the release of copper ions, such as Cu2+, into the water. These released copper ions can then react with other components present in the water, particularly carbonates and bicarbonates, which are key contributors to water’s natural alkalinity. This reaction often results in the formation of insoluble compounds like copper carbonates.
While some sources suggest that storing water in copper vessels might slightly increase pH, the primary effect of copper in plumbing systems is not to raise the water’s alkalinity. In fact, the presence of metal ions from corrosion can, under specific chemical conditions, sometimes lead to a slight decrease in pH. The main concern is not a change in alkalinity but rather the presence of dissolved copper in the water itself.
Factors Affecting Copper Leaching
Several environmental and water chemistry factors influence how much copper leaches into water. Water with a lower pH tends to be more corrosive to copper pipes. This acidic water can dissolve copper more readily, leading to higher copper concentrations. Soft water, which has a low mineral content, is generally more corrosive to copper than hard water because it lacks the protective mineral scales.
Dissolved oxygen in water can accelerate copper corrosion. Higher water temperatures also contribute to increased copper leaching. Newer pipes may leach more copper until a protective oxidized coating forms on their interior surfaces.
Understanding Copper Levels in Water
The presence of copper in water, even if it doesn’t make it alkaline, can lead to issues. Elevated copper levels can impart a metallic or bitter taste, especially after water has been stagnant in pipes. Blue-green stains on sinks, fixtures, and laundry are another common indicator. These stains result from the corrosion of copper pipes, where copper tainted water evaporates and leaves behind copper oxide.
While copper is an an essential nutrient, excessive levels can be harmful. Short-term exposure to high copper levels can cause gastrointestinal distress. Long-term exposure to elevated copper can affect the liver or kidneys. The U.S. Environmental Protection Agency (EPA) has established an action level for copper in drinking water at 1.3 milligrams per liter (mg/L), which serves as a trigger point for corrective actions by water systems if exceeded in more than 10% of samples.