- Home|Search


Water quality

Tap Water in Yokohama

We drew up a plan to ensure the quality and credibility of our tap water inspections so that safe and clean water can be supplied to residents. Based on this plan, we inspect certain articles that we set in addition to water quality standards and water quality management of tap water as well as purification plants and water sources.

1. Articles of Water Quality Inspection

(1) Water Quality Standard - 50 articles

It is set based on Article 4 of the Waterworks Law, in which water supplied from waterworks is required to meet necessary conditions. It shows the required level of water quality from the perspective of residents' health and the necessity of water in residents' everyday life, for example, tap water must not have any impact on residents' health and residents' life by low-quality water releasing unusual odors or leaving stains on laundry.

(2) Water Quality Management - 24 articles

The target level is set to ensure the continuous supply of safe water considering things necessary to maintain water quality.
To ensure safe tap water, articles on toxic substances that are present in tap water to a very small degree have been included. These articles were not included in previous inspections because those inspections were totally provisional. Articles on substances which are currently well within safety standards, but are expected to increase in the future, have also been included.

(3) Our Own Water Quality Inspection - 13 articles

These are used for inspecting raw water contamination and process management in purification, confirmation of safety and quality of water served in Yokohama and so on.

2. Water Quality Inspections and Inspection Sites

The Water Quality Inspection Division conducts the following inspections except for inspections at purification plants.

(1) Taps (Hydrants)

For water from purification plants or regional waterworks organizations at 22 sites in 18 administrative districts in Yokohama, inspections are conducted every month on articles considered necessary in terms of water quality standard and water quality management that require inspections at least 1 time under the law such as articles on pathogenic microorganisms in water and the basic conditions of water. Other water quality standard, water quality management and our own water quality inspections are conducted at least 4 times a year as set in the Water Quality Inspection Plan. In addition, we conduct daily inspections stipulated under the law aiming at maintaining sanitary conditions at 50 sites in Yokohama.

(2) Purification Plants

Inspections of water quality standard and water quality management are carried out 4 times annually to make sure that process management of purification is appropriate to provide safe and high quality water to residents. Basic conditions such as pathogenic microorganisms, turbidity, color, tastes, odors and residual chlorine are inspected everyday and the status of chloride ion and organic matters are checked once a month.

(3) Water Source

Monthly inspections are carried out at water intake points of the Doshi River, Sagami Lake,
the Banyu River and the upper reaches of those because water quality at those areas affects the purification process to distribute safe and high quality water.

▲ top

     City of Yokohama Home > Yokohama Waterworks Bureau Home  > Water quality

水道局噴水マーク Yokohama Waterworks Bureau, Water Quality Inspection Division - Created on 2011, 1, 20 - Updated on 2011, 1, 20
Tel: 045-633-0130 - FAX: 045-664-6774
© 1998-2014 City of Yokohama. All rights reserved.