The pH of Drinking Water in Malaysia

The pH of Drinking Water: Defining the Normal Range

Groundwater is a vital resource necessary for all aspects of human and ecosystem survival. Consequently, the quality of drinking water is one of the greatest factors affecting human health and is an indispensable resource.

Understanding the pH Scale

The term pH, which stands for "potential of hydrogen," is a measure of the concentration of hydrogen ions H and hydroxide ions OH in a solution. It is one of the most important operational water quality parameters, although pH itself usually has no direct, immediate impact on consumers' health.

The pH scale ranges from 0 to 14. Pure water, at a standard temperature, has a pH of 7, which is defined as neutral. Any substance with a pH value less than 7 is considered acidic, and a value greater than 7 is considered alkaline (or basic). The pH value is used to measure the acid–base equilibrium, which in most natural waters is controlled by the complex carbon dioxide–bicarbonate–carbonate equilibrium system.

What is the "Normal" pH for Drinking Water?

When referring to the "normal" pH of drinking water, the focus shifts from the theoretical neutral point (7) to the functional and safe range mandated by health organizations worldwide.

While pH 7 is the neutral point, finished drinking water is rarely exactly 7.0 due to dissolved minerals and gases. Generally, the acceptable or normal range for safe and efficient public water supply is considered to be between 6.5 and 9.5. Many national and international guidelines, including those from the World Health Organization (WHO), often cite a range that begins at 6.5 or 7.0 and extends up to 8.5 or 9.0.

This wide operational range is important for several key reasons:

• Corrosion Control: Water that is too acidic (below pH6.5) can be corrosive, dissolving metals like lead and copper from pipes and fixtures, which is a significant health concern.

• Optimal Treatment: pH is critical for water treatment processes; for example, many chemical disinfectants, like chlorine, work optimally within a specific pH window.

• Aesthetics: Water with a pH significantly outside this normal range may have an objectionable metallic or bitter taste and can cause scaling or soap residue.

In summary, while pH 7 is the chemical definition of neutrality, the "normal" and acceptable pH for tap water is typically the safe operational range defined by water quality standards, generally spanning 6.5 to 9.5, which ensures the water is not corrosive and remains safe and palatable.