What should be the pH value of drinking water? | The Daily Star
12:00 AM, September 06, 2015 / LAST MODIFIED: 12:00 AM, September 06, 2015

What should be the pH value of drinking water?

Remember the time in science class when you did that experiment with litmus paper and it turned red when you put it on a lemon and blue in soapy water? That was probably your first experiment into the wondrous science of pH.

The indicator for acidity and alkalinity is known as the pH value. A pH value of 7 means a substance is neutral. The lower value indicates acidity, and a higher value is a sign of alkalinity. To better understand the range in pH, take a look at these examples: apple juice 3, orange juice 3.5, coffee 5.5, milk 6.2, baking soda 8.5, soapy water 10, bleach 12.

So, what does pH mean for water?

Basically, the pH value is a good indicator of whether water is hard or soft. The pH of pure water is 7. In general, water with a pH lower than 7 is considered acidic, and with a pH greater than 7 is considered basic. The normal range for pH in surface water systems is 6.5 to 8.5, and the pH range for groundwater systems is between 6 to 8.5. Alkalinity is a measure of the capacity of the water to resist a change in pH that would tend to make the water more acidic. The measurement of alkalinity and pH is needed to determine the corrosiveness of the water.

Effects

Consuming excessively acidic or alkaline water is harmful, warns the Environmental Protection Agency (EPA). Drinking water must have a pH value of 6.5-8.5 to fall within EPA standards, and they further note that even within the acceptable pH range, slightly high- or low-pH water can be unappealing for several reasons.

High-pH water has a slippery feel, tastes a bit like baking soda, and may leave deposits on fixtures, according to the EPA website. Low-pH water, on the other hand, may have a bitter or metallic taste, and may contribute to fixture corrosion.

Expert insight

Wilkes University points out a further problem associated with drinking water and pH: High-pH water is often hard. They note that hard water “does not pose a health risk, but can cause aesthetic problems.” Among problems associated with hard water, they list formation of scale on fixtures, a bitter flavor, difficulty getting soaps to lather, and decreased water-heater efficiency. They suggest that water can be softened with ion-exchange water-softening devices.

According to a Wilkes University study, the association of pH with atmospheric gases and temperature is the primary reason why water samples should be tested on a regular basis. The study says that the pH value of the water is not a measure of the strength of the acidic or basic solution, and alone cannot provide a full picture of the characteristics or limitations with the water supply.

While the ideal pH level of drinking water should be between 6-8.5, the human body maintains pH equilibrium on a constant basis and will not be affected by water consumption. For example, our stomachs have a naturally low pH level of 2 which is a beneficial acidity that helps us with food digestion.

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