Possible test procedures.

Overview of the various procedures for measuring the pH value of water and which water types they are each suitable for.

Litmus and test strips

These indicators are intended for urine. Only conditionally suitable for tap water and mineral water. There are considerable measurement tolerances. For distilled water or water from reverse osmosis systems this procedure is not suitable, since ions must be present in the test solution! Usually a value around 5 is displayed, however this is incorrect! A minimum conductivity of 200-300 µS is required.

Indicator solutions

These indicators are suitable for tap water and mineral water. However, there are also measurement tolerances here. For distilled water or water from reverse osmosis systems this procedure is not suitable, since ions must be present in the test solution! Usually a value around 5 is displayed, however this is incorrect! A minimum conductivity of 200-300 µS is required.

Digital pH value measuring devices

These measuring devices (costing between 50€ and 140€) are suitable for tap water and mineral water. There are small measurement tolerances, however the measuring device must be calibrated with buffer solutions (pH 4 and pH 9) before each measurement. For distilled water or water from reverse osmosis systems this procedure is not suitable, since ions must be present in the test solution! Incorrect measurement results are displayed! A minimum conductivity of 200 µS is required.

Laboratory measuring devices

These measuring devices (costing between 200€ and 1,000€) are suitable for tap water and mineral water. There are only very small measurement tolerances, however the measuring electrode must be calibrated with buffer solutions (pH 4 and pH 9) before each measurement and then stored in a special solution. For distilled water or water from reverse osmosis systems this procedure is not suitable, since ions must be present in the test solution! Incorrect measurement results are displayed! A minimum conductivity of 100 µS is required.

Special laboratory measuring devices

These measuring devices are suitable for tap water and mineral water. There are only very small measurement tolerances, however the measuring electrode must be calibrated with buffer solutions (pH 4 and pH 9) before each measurement and then stored in a special solution. These are specially suitable for distilled water or water from reverse osmosis systems, since no ions need to be present in the test solution! No minimum conductivity is required.

• pH value
• redox
• microsiemens