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Japan’s Sewage & Water Supply Systems


When you turn on a tap, have you ever wondered what proportion of water leaks out of the pipes it must travel through to get from the waterworks facility to the tap you have just opened? This proportion is called the “leakage rate,” and looking at waterworks facilities around the world, those with high leakage rates record losses of between 30–40% before the water reaches the tap. Even in large cities with an advanced waterworks system, the average leakage rate is around 10%. Leaking water is an everyday occurrence in almost all of the water pipes across the entire world.

In Tokyo, however, the leakage rate is tiny at just 3.6%.

This figure was first made public at the second Large Cities Climate Change Summit, in 2007, and its low level shocked the summit delegates, gathered from around the world.

By this 3.6% leakage rate, Tokyo prevented water leakage equivalent to the same amount of water as that used in a year by a city of 3.5 million that has the avarage leakage rate; this comparison should indicate how important such figures are. Japanese cities other than Tokyo also have a low leakage rate. Even those with higher rates generally maintain ratios of less than 10%, and the national average is around 7%. These figures are dropping on an annual basis (In 2010, the leakage ratio for Tokyo was 3.1%).

For regions that are lacking in water resources, being able to secure even just a little more water for domestic use can be a question of life and death; instability in water supply is an extremely series issue. The outstanding waterworks system technology that Japan has developed can greatly benefit society in such countries.

Well-designed sewage systems are also an extremely important technology in terms of recycling and reusing our precious water resources. Here, we introduce Japan’s waterworks and sewage systems.


Leakage Rates of World Metropolises

CityPopulation served by piped water supplyLeakage Rates
London7 million26.5%
Berlin3.5 million5%
Turin1.2 million25%
Istanbul11.5 million25.2%
Madrid3.12 million10.5%
Moscow10.4 million9.9%
Cairo16 million20%
Mexico City8.6 million35%
Hong Kong6.75 million26%
Incheon2.25 million17%
Tokyo12.13 million3.6%

(Data by Water Security Council of JAPAN,  "Final Report" July,2008)