■What are the guideline values for circulating water? For circulating cooling water using open cooling towers, the values for the standard items are as follows: 1. pH (25°C): 6.5 to 8.2 2. Electrical conductivity (25°C): 80 mS/m (800 μS/cm) or less 3. Chloride ions: 200 mg/L or less 4. Sulfate ions: 200 mg/L or less 5. Acid consumption (pH 4.8): 100 mg/L or less 6. Total hardness: 200 mg/L or less 7. Calcium hardness: 150 mg/L or less 8. Ionic silica: 50 mg/L or less Acid consumption and hardness are expressed as values converted to calcium carbonate. ■Are the issues being examined different for each item? The table indicates whether each item is related to corrosion or scale formation. Chloride ions and sulfate ions are associated with corrosion, while hardness, silica, and acid consumption are on the scale formation side. pH and electrical conductivity are related to both. ■Are the guidelines for makeup water stricter? For makeup water, the guidelines are more stringent, with electrical conductivity of 30 mS/m or less, chloride ions of 50 mg/L or less, total hardness of 70 mg/L or less, and ionic silica of 30 mg/L or less.

■What can you see compared to the supply water?! Assuming that the supply water has the maximum water quality, the margin for the circulating water is calculated to be about 2.7 times for electrical conductivity, 4 times for chloride ions, and about 1.7 times for silica. ■Which items are measured every month? In building maintenance operations, pH and electrical conductivity are measured monthly during the operation period to ensure they meet guideline values. If they do not match, all items are measured to investigate trends in corrosion and scale formation. ■Rules for sampling and recording Sample collection follows JIS K 0094, and analysis and judgment follow JIS K 0101. The date, time, location, results, implementer, and method of sampling and measurement are also recorded. ■Guidelines for residual chlorine and disinfection concentration The reference value for residual chlorine is below 0.3 mg/L. On the other hand, maintaining residual chlorine at 2 to 5 mg/L can achieve a disinfecting effect against Legionella bacteria. However, chlorine has a strong oxidizing power, and if added in high concentrations all at once, it can easily damage heat exchangers and piping. A method of continuous addition at low concentrations is preferred. We also offer consultations on how to measure water quality and select water treatment chemicals. Please feel free to contact us first.