Maintenance of cooling towers

The cooling tower is used in combination with the air conditioner of the building.
If the cooling tower is not properly maintained, the proliferated Legionella spp. may be scattered around, causing large-scale outbreaks of Legionella disease.

The cooling tower should be managed as follows.

(1)　Water that conforms to the water quality standards stipulated in Article 4 of the Water Supply Act shall be used for cooling water in the cooling tower.
(2)　Conduct chemical cleaning (circulating fungicides to the cooling water system according to equipment conditions) before starting operation. In addition, it is desirable to carry out the operation at the end of operation.
(3)　The following management is performed during the operation period.
　A. Control the number of bacteria using anti-regionella drugs.
　B. In order to prevent excessive concentration of cooling water, forcibly drain the cooling water in a timely manner.
　Water treatment with chemicals is performed to prevent scale, corrosion, and slime.
　　　※　With regard to the handling of drugs, pay close attention to precautions for use.
　(D) Clean the cooling tower regularly once a month.
　　　※　At the time of cleaning, let workers wear protective masks, protective glasses, rubber gloves, etc.
　(E) The cooling tower shall be inspected regularly once a month.
　　　Inspection items: Stain, damage, clogged conditions of lower tanks, watering equipment, filling materials, eliminators, etc.
　　　　　　　　Operational status of ball taps, chemical injection devices, automatic blowers, blowers, and electric motors

Let's carry out water quality inspection of Legionella spp. according to the operating status of the cooling tower.

※1 The test method shall be a culture method based on the filtration concentration method or the cooling centrifugal concentration method as indicated in “Regionella spp. Testing Methods for Bathtub Water, etc. in public bath” (September 19, 2019, Notification of Director Health Sanitation Division, Pharmaceutical and Health Bureau, Ministry of Health, Labour and Welfare).

※2 The guideline value is based on the fourth edition of the Legionellosis Prevention Guidelines.

Enlightenment flyer "Appropriate maintenance of cooling tower" (PDF: 682KB)

If the value is exceeded, take the following actions according to the detection results and immediately contact Health and Welfare Center Health Sanitation Division in the district where the facility is located.
In addition, investigate the cause of the growth of Legionella spp., and review the maintenance method to prevent recurrence.
　

• 　Legionella spp. test guideline value excess report (reference style) [PDF (PDF: 144KB) (PDF: 144KB)] [EXCEL (Excel: 24KB) (Excel: 24KB)]

　　[Contact]

　List of consultation desks related to environmental hygiene in Health and Welfare Center Health Sanitation Division

Legionellosis was named in 1976 when it was discovered as a group pneumonia at a local military assembly in Philadelphia, USA.
It was estimated that the source of infection at this time was the cooling tower of the hotel where the venue was held.
In Japan, there have been cases of infection that are thought to be caused by cooling towers.

• Cases of Legionellosis outbreaks caused by cooling towers of hospitals (National Institute of Infectious Diseases website) (outside site)
• Experience cases of Legionellosis accumulation suggesting exposure from cooling towers (1st report)-Epidemiological surveys and facility response-(National Institute of Infectious Diseases website) (outside site)