Does the pH of water matter?

The first thing you need to keep in mind is that the pH value of water 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.

In general, water with a pH below 6.5 could be acidic, soft, and corrosive.

Acidic water could contain metal ions such as iron, manganese, copper, lead, and zinc. In other words, acidic water contains elevated levels of toxic metals. Acidic water can cause premature damage to metal piping, and have associated aesthetic problems such as a metallic or sour taste. It can also stain laundry and cause "blue-green" color staining on sinks and drains. More importantly, there are health risks associated with these toxins.

On the other hand, water with a pH above 8.5 could indicate that the water is hard and extremely alkaline.

Hard water is water that has high mineral content (in contrast with "soft water"). Hard water is formed when water percolates through deposits of calcium and magnesium-containing minerals such as limestone, chalk and dolomite.

Hard water does not only pose a health risk, but can also cause aesthetic problems. These problems include an alkali taste to the water (making that morning coffee taste bitter!), formation of scale deposits on dishes, utensils, and laundry basins, difficulty in getting soaps and detergents to lather, and the formation of insoluble precipitates on clothing.

Does the pH of water change the pH in the human body?

While the ideal pH level of drinking water should be between 6.5 and 8.5, the human body maintains pH equilibrium on a constant basis and such values are not affected by the consumption of water that is within that range. For example, our stomachs have a naturally low pH level of 1.5, which is a beneficial acidity that helps us with food digestion.

The health risks arise from the possible presence of heavy metals, contaminants and hard mineral deposits in water as indicated by its pH, rather than the pH value on its own.

AUTHOR: Alex Ruani, Research Director

Updated on: 15/10/2026