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Water quality inspection items

Last Updated October 4, 2024

Please refer to the Ministry of the Environment web page (outside site) for the standard values of each item.

Water quality standard items

The Water Supply Law stipulates water quality standards for 51 items as requirements for water quality to be provided by water supplied by water supply.
Tap water supplied by water utilities must conform to this standard.
Water quality standard items are divided into items related to health and items related to the properties that tap water should have.

“Items related to health” No. 1-31

Standards have been set so that people do not drink tap water for a lifetime (generally 70 years) and do not affect their health.

“Items related to the properties that tap water should have” No. 32-51

Standards have been set to prevent color, turbidity, smell, etc. when using tap water as domestic water, or to prevent management problems of water supply facilities such as corrosiveness.

Commentary on 51 water quality standards

Water quality management target setting items

There is a certain detection in tap water, but it was not detected as a water quality standard because the toxicity evaluation was provisional, or it has not been detected in tap water at a concentration that would be used as a water quality standard until now. As items to be noted in water quality management, such as those that may be detected at a higher concentration, target values have been set from the viewpoint of ensuring the safety of tap water in the future.

Items to be considered

Items that cannot be classified into water quality standard items and water quality management target setting items because the toxicity evaluation is not determined or the amount of water in purified water is unknown.

For inquiries regarding water supply, please contact the Water Works Bureau Customer Service Center.

Water Works Bureau Customer Service Center

Telephone: 045-847-6262 Fax: 045-848-4281
※Please be careful not to make a mistake.

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Inquiries to this page

Water Quality Division, Water Works Bureau Water Purification Department

Telephone: 045-371-5656

Telephone: 045-371-5656

Fax: 045-371-6942

Email address: su-suishitsu@city.yokohama.lg.jp

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Page ID: 114-928-146

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