This standard specifies the electrode method for the determination of pH value in water. It is suitable for the determination of pH value in surface water, groundwater, domestic sewage and industrial wastewater. The measurement range is 0~ 14. The principle of the method is to determine the pH value by measuring the electromotive force of the battery, usually consisting of a reference electrode and a hydrogen ion indicator electrode. In terms of interference and elimination, the Color, turbidity, colloidal substance, oxidation agent and reducing agent of water will not interfere with the determination, but errors will occur in extremely acidic or alkaline solutions, and corresponding measures need to be taken. When measuring samples with high electrolysis quality, pH electrodes suitable for high ionic strength should be used. At the same time, the temperature affects the potential of the electrode and the ionization of water equilibrate, so the instrument should have a temperature compensation function.