The quality of tap water is monitored by various measurements, including the potential of hydrogen, or pH, which indicates whether water is acidic or alkaline. This measurement is important for understanding the chemical behavior of water and its tendency to interact with the materials it contacts. A balanced pH level influences water quality, affecting everything from taste to the longevity of your home’s plumbing.
Understanding the pH Scale
The pH scale is a logarithmic measurement that quantifies the concentration of hydrogen ions in a solution, determining its acidity or basicity. The scale spans from 0 to 14, with 7 being neutral, the value of pure water at room temperature.
Solutions with a pH below 7 are acidic, meaning they have a higher concentration of hydrogen ions. Substances with a pH above 7 are classified as basic or alkaline. The logarithmic nature of the scale means that each whole number represents a tenfold change in acidity or alkalinity; for instance, water with a pH of 6 is ten times more acidic than water with a pH of 7.
Ideal and Regulated pH Levels
The United States Environmental Protection Agency (EPA) recommends that the pH of public drinking water fall between 6.5 and 8.5. This standard is not set for direct health concerns but is categorized as a secondary drinking water regulation.
Secondary standards are non-mandatory guidelines addressing the aesthetic and technical quality of the water. While water outside the 6.5 to 8.5 range is safe to drink, extreme pH is monitored because it can cause issues like unpleasant taste or odor. This range guides public water systems to ensure the water is acceptable to consumers and prevents problems within the distribution system.
The Impact of pH on Water Quality
A pH level that is too low results in corrosive water, posing a threat to metal plumbing systems. Acidic water (pH below 6.5) slowly dissolves metals in pipes, leading to leaks and repair costs. As pipes corrode, harmful metals like lead, copper, and zinc can leach into the drinking water, creating a health hazard. Consumers may notice a metallic or sour taste, and blue-green staining on fixtures often indicates copper corrosion.
Conversely, water that is too alkaline (pH above 8.5) can cause mineral deposits, known as scaling, to build up inside pipes and appliances. Scaling reduces water flow and lessens the efficiency and lifespan of water heaters and other appliances. A high pH can also decrease the effectiveness of chlorine disinfectants used by water treatment facilities. Highly alkaline water can sometimes have a slippery feel and a bitter or soda-like taste.
Factors Influencing Local Tap Water pH
The pH of tap water is not uniform and is determined by the source water and the treatment processes applied by the utility. The geological composition of the area plays a role; water sourced from limestone bedrock often has a higher mineral content, resulting in naturally alkaline water. In contrast, water from soft sources like rain or snowmelt, particularly in areas with granite, tends to be more naturally acidic.
Water treatment facilities actively manage the pH to ensure it falls within the recommended range, primarily to control corrosivity and prevent damage to infrastructure. Utilities often add chemical compounds like lime or soda ash to acidic water to raise the pH and stabilize the water. Adjusting the water to be slightly alkaline before distribution creates a protective layer on the interior of pipes, which helps reduce the leaching of metals into the water supply.