Alkalinity in water is a chemical property that consumers often seek to reduce due to its practical effects. Alkalinity refers to a water source’s capacity to neutralize acids, a trait linked to its mineral content. Water with high alkalinity often presents as having a slightly metallic or bitter taste. The minerals contributing to high alkalinity are also a common cause of scaling, the hard, chalky deposits that accumulate inside pipes, appliances, and fixtures.
Defining High pH and Water Hardness
Understanding water chemistry requires separating the concepts of pH, alkalinity, and hardness, which are often mistakenly used interchangeably. The pH scale measures the water’s acidity or basicity, with values above 7 indicating a basic, or “alkaline,” condition due to a low concentration of hydrogen ions.
Alkalinity is the water’s buffering capacity, representing its ability to resist changes in pH when an acid is introduced. This buffering is provided by dissolved compounds such as bicarbonates, carbonates, and hydroxides. High concentrations of these ions mean the water is highly buffered and will maintain a high pH more easily.
Water hardness is a separate measurement that quantifies the concentration of dissolved multivalent metal ions, mainly calcium and magnesium. These minerals are the principal cause of scaling and soap scum. While hardness and alkalinity are often related, a water softener only addresses hardness by exchanging these metal ions for sodium, leaving the alkalinity largely unaffected.
Immediate Solutions for Small-Scale Adjustment
For immediate, small-scale adjustment of highly alkaline water, such as for drinking, there are temporary, low-cost methods. A simple option involves adding a small amount of a natural acidulant directly to the water. Adding a few drops of fresh lemon juice or white vinegar introduces a mild acid that reacts with and neutralizes some of the alkaline compounds, thereby lowering the pH for immediate consumption.
Boiling water is sometimes suggested, but its effect is limited to only one component of water quality. Boiling causes calcium and magnesium bicarbonates, which are responsible for temporary hardness, to precipitate out as solid scale. This process reduces temporary hardness but does not significantly affect the total alkalinity or permanent hardness components of the water.
Standard countertop filtration pitchers, which use activated carbon filters, are highly effective at removing contaminants like chlorine and improving taste and odor. However, activated carbon works through adsorption and does not remove the dissolved mineral ions responsible for high alkalinity or high pH. Therefore, these filters offer little practical change in the water’s alkaline chemistry.
Systemic Methods for Water Treatment
For a permanent, whole-house solution to reduce high alkalinity, specialized water treatment equipment is necessary.
Reverse Osmosis (RO)
The most common and effective method for removing the dissolved solids that cause high alkalinity and hardness is Reverse Osmosis (RO). An RO system forces water through a semi-permeable membrane that filters out virtually all dissolved inorganic solids, including bicarbonate and carbonate ions. The resulting product is highly purified water with a low concentration of minerals, which also reduces the water’s buffering capacity and pH.
Distillation
Distillation reduces alkalinity by simulating the natural rain cycle. The water is heated to steam, leaving all non-volatile minerals and dissolved solids behind, and the steam is then condensed back into liquid form. This process yields nearly mineral-free water, which is often slightly acidic due to the absorption of carbon dioxide from the air.
Chemical Neutralization
Chemical neutralization, often called acid injection, directly lowers the water’s pH by introducing a mild acid into the water line. This process uses an injection pump to feed a measured amount of an acidic solution, such as a food-grade mineral acid or carbon dioxide. The acid reacts with and neutralizes the alkaline compounds, but requires continuous monitoring to ensure the water’s final pH remains within a safe, neutral range and does not become corrosive.
Ion Exchange Systems
Ion exchange systems, commonly known as water softeners, are highly effective for water hardness but do not target alkalinity. These systems swap the scaling-causing calcium and magnesium ions with non-scaling sodium or potassium ions. While hardness is removed, the bicarbonate and carbonate ions that contribute to the water’s overall alkalinity remain.