What is a water quality test for a water storage tank? Items to check after cleaning [Basic Knowledge]

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■Which items should be checked? The items and criteria to be verified are as follows: 1. Residual chlorine: 0.2 mg/L or more for free chlorine, 1.5 mg/L or more for combined chlorine 2. Color: 5 degrees or less 3. Turbidity: 2 degrees or less 4. Odor: Not abnormal 5. Taste: Not abnormal ■Is 0.2 mg/L high?! According to the Water Supply Act enforcement regulations, the required free residual chlorine in tap water is usually 0.1 mg/L or more. However, when there is a significant risk of the supplied water being contaminated with pathogenic microorganisms, the values are raised to 0.2 mg/L or more for free chlorine and 1.5 mg/L or more for combined chlorine. The standard after cleaning is the same as this higher value. ■What if the standards are not met? If the standards are not met, the cause will be investigated and necessary measures will be taken. The date of cleaning, the name of the implementer, the details of the work, the status of inspections and repairs, and the names of the disinfectants used will be recorded in a ledger. ■Tools for on-site measurement Residual chlorine measurement is conducted using the DPD method or a method with equivalent or higher accuracy. Registration for water tank cleaning services also requires the possession of a colorimeter, turbidity meter, and residual chlorine measuring device as stipulated by the enforcement regulations.

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■What about water tanks with a capacity of 10 cubic meters or less? Facilities with a total capacity not exceeding 10 cubic meters are classified as "small-scale water tank systems" and are subject to national sanitation measures for drinking wells, etc. They should be managed according to the management standards for simple dedicated water supply systems, with inspections of color, odor, taste, color degree, and turbidity at the tap conducted at least once a year, as well as checking for the presence of residual chlorine. ■Check the regulations of water supply operators! The Water Supply Act stipulates that water supply operators define the responsibilities of the water tank system installers in their supply regulations. The enforcement regulations outline the management standards and inspection of management conditions from the installer’s side, and guidance, advice, and information provision to users from the water supply operator’s side. Even if the capacity is small, be sure to check the supply regulations and municipal guidelines. ■Cleaning and inspection together For specific buildings, in addition to cleaning, regular inspections of the free residual chlorine at the water supply taps are also conducted. Confirmation after cleaning is a milestone that contributes to daily management of residual chlorine. At Torii, you can request a continuous service that includes inspection of the exterior of the water tank, cleaning and disinfection inside the tank, and subsequent water quality testing. Please feel free to consult with us first.