Water quality

For tap water, the government has established tap water quality standards that fully consider safety, and water utilities across the country are obliged to comply with and inspect them.
According to Article 4 of the Water Supply Law, there are six requirements for tap water quality standards, such as not being polluted by pathogenic organisms and not toxic substances. Specifically, 51 standard values are set in the ministerial ordinance on water quality standards. About water quality standard, please see explanation (PDF) of 51 water quality standard items in page of water quality inspection item or page 19 of the same name file (PDF) in page of water quality inspection plan.
In Yokohama City, we independently set water quality management values that are stricter than national standards, and by properly managing water quality from water sources to faucets, we supply safe and high quality water to customers.

As for water source or water intake place, please see the same name file (PDF) of page of water source of Yokohama-shi. About water supply area, please see figure of page of water examination result or file (Excel) of hydrant (faucet) inspection result of the same page.

Water quality tests are regularly conducted at the entrances and exits of each of the three water purification plants, and at 15 fixed faucets such as parks in the city. In addition, 43 water measurement facilities are installed throughout the city, and "chromaticity", "turbidity", and "residual chlorine" are inspected continuously for 24 hours a day. For more information, please see the following page.

Please see file (Excel) of each test result of hydrant (faucet) in page of water examination result and water purification plant.

Please see commentary (PDF) of 51 water quality standard items in page of tap water quality standard.

Please see the 39th "calcium, magnesium, etc. (hardness)" of the hydrant (faucet) test result file on the water test result page.

For test results, see the test results of organic fluorine compounds (PFAS), and for frequently asked questions and answers, see the page on organic fluorine compounds (PFAS).

In Water Works Bureau, we go to the homes of customers who wish to conduct water quality tests and conduct free water quality tests at the faucet.
To apply, please contact the Water Works Bureau Customer Service Center.
In addition, in large-scale condominiums and buildings, etc., where the effective capacity of the receiving tank exceeds 100 cubic meters, etc., corresponds to a dedicated water supply, a water supply technology manager in charge of technical work related to water supply management is set up. Because it is, it is excluded from this water quality inspection.

①If the water is white, pour it into a transparent container and leave it for a while. If there is no sediment and it becomes transparent from below, the air dissolved in tap water becomes fine bubbles, and it is considered that the water looks white. In this case, there is no problem for drinking. If there is sinking and it does not become transparent, stop drinking and apply for a water test.
②If the water is red or yellow, the water may be colored by gradually rusting the inner surface mainly with an old iron pipe. Drinking is acceptable if you wash a bucket about a bucket and become colorless and transparent. If you are worried, please consider applying for a water quality test.
③If water colored in black or blue comes out, stop drinking and apply for a water test.

There is an example below. If you are worried, please consider applying for a water quality test.

If a lead water pipe is used for your home water pipe, a small amount of lead may dissolve into the accumulated tap water. Please use the first water in the morning except for drinking. There is no health problem with drinking water after drinking.

• Response to lead water pipes

The management and water quality of water supply facilities from receiving tanks to faucets in condominiums and buildings was under the jurisdiction of the Health and Social Welfare Bureau. However, due to hygiene problems caused by inadequate management, the Water Supply Law was revised in June 2001, and the Water Works Bureau, which supplies water, was involved in the management of water tanks.
In Yokohama City, the Water Supply Ordinance was revised in December 2002, and the following measures are taken.
（1） In response to requests from users of water tanks (residents), Water Works Bureau will conduct water quality tests at the faucet of each house free of charge and inform them of the results.
（2） As a result of the water quality inspection at the faucet, if there is a problem with the safety of the water quality, jointly conduct water quality inspection and inspection in the water receiving tank in cooperation with the Medical Care Bureau, and it is recognized that it is necessary to manage the water tank water supply If so, we will give guidance, advice and recommendations to the installer of the water tank water supply. Water quality inspections are not included in the Water Supply Law Enforcement Regulations, but are not included in the Water Supply Law.
（i） High interest of users in water quality
（ii） Equalize services with users of detached houses, etc.
（iii） Considering that water quality inspection is necessary to judge the management situation of water tank water supply, we made the regulations as Motoichi original correspondence.
In addition, the contents of the management responsibility of the water tank water supply installer based on the Water Supply Law and the ordinances under the jurisdiction of the Medical Care Bureau ("Ordinance on Securing Safe and Sanitary Drinking Water in Yokohama City Simple Water Supply and Small Water Tank Water Supply") remain unchanged.
However, in the case of large-scale condominiums and buildings with an effective capacity of the receiving tank exceeding 100 cubic meters, etc., a water supply technology manager in charge of technical work related to water supply management is set up. Because it is excluded from this water quality inspection.