What is the pH value of tap water?

According to the Drinking Water Ordinance, the pH value of tap water must be within certain limits. It explains where the limit values are, which factors have an influence on the pH value of tap water, and how and whether the pH value affects health.

Limit values for the pH value

The Drinking Water Ordinance provides a limit value of 6.5 for the pH value of tap water on the lower side. According to the German Drinking Water Ordinance 2001, a value of 9.5 is permitted as the maximum pH value for drinking water.

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The European guidelines for drinking water take the values somewhat stricter. A maximum value of 8.5 at the upper limit is recommended here. The value of 6.5 as the minimum pH value also applies there.

For bathing water (water that is suitable for bathing in bodies of water and bathing facilities), however, different values apply: The EU allows values between 6.0 and 9.0, according to DIN the value must be between 6.5 and 7.8. In terms of pH, bathing water is still largely drinking water.

Factors influencing the pH value of water

A large number of factors influence the pH value of water.

Mineralization and contained substances

The degree of mineralization and the type of minerals occurring have a fundamental influence on the pH value.

In general, the higher the amount of minerals in drinking water, the more basic water becomes. That is why many medicinal waters often have an alkaline effect on the body.

High water hardness, i.e. a high occurrence of Ca + and Mg + ions as hardness components in the water, can also indirectly increase the pH value. For this, however, certain conditions must be given.

High water hardness can bind acids in the water and thus increase a low pH value.

Carbon dioxide content

A high amount of dissolved carbon dioxide in the water will lower the pH. This is the case with rainwater, for example. It removes carbon dioxide from the air and does not contain any hardeners that can buffer these effects.

Rainwater is therefore comparatively acidic. It has a natural pH of around 4.7 to 5. Since the air pollution from sulfur oxides and other materials was reduced, its pH value has risen again.

Tap water can also contain different levels of carbon dioxide, depending on its source. This is also responsible for a change in the pH values.


The pH value is strongly dependent on temperature. Therefore, when specifying the pH value and taking measurements, always ensure that the exact water temperature is specified during the measurement.

Health effects of different pH values

The pH value within the limit ranges has no direct impact on human health. Since water is only a weakly buffered acid or base, the pH value of water changes very easily according to its environment.

However, drinking water with a pH value close to 7.0 is often recommended. But this is in contrast to the mineral contents that are often recommended.

Tips & Tricks It can be assumed that the more natural the water, the greater the health effect. Artificial technical changes can often have complex, hardly foreseeable consequences.