Tokyo has one of the most efficient water systems in the world. Its method of detecting and repairing leaks has halved the amount of water wasted by the City in the past ten years from 150 million m3 water to 68 million m3 water. Its' focus on same-day-repair work - has helped to drastically reduce the leakage rate - from 20% in 1956 to 3.6% in 2006, as well as reduce carbon dioxide emissions by about 73,000 t CO2 annually.

What is it?

The Bureau of Waterworks program aims to manage essential water resources in the most efficient way, conducting prevention and early repair of leakage. This stops collateral damage, which can potentially occur as a result of the leakage, such as subsidence of roads and muddying of the water.

How does it work?

Tokyo's water supply serves about 5 million m3 of water everyday to 12million citizens in Tokyo. The water is supplied by four rivers Tone, Ara, Tama and Sagami, which flow into the Metropolitan area. The untreated water is taken from these rivers and purified through three processes - coagulation, sedimentation and filtration at local plants. It is then pressurised and supplied to customers as tap water through underground pipelines. The total length of distribution pipes is about 25,262 km in 2005.

Water leakage

Control of water leakage is one of the most critical aspects of Tokyo's system. Importantly, all repair work for the leakages takes place on the same day. Efforts are made to carry out early detection and repair of underground leakage, this has been achieved by replacing pipes and improving pipe materials, i.e., from cast iron to ductile cast iron for distribution pipes. In 1985 there were about 58,000 cases of leakage repair - this dropped to about 21,000 in 2005.

Most leakage is caused by:

  • 97% cracked or corroded pipes service pipes
  • 3% aging distribution pipes

In addition to routine checks and repairs, renewal of aged pipes and replacement of lead feeder pipes with stainless steel pipes is a major priority. This has succeeded in reducing huge amounts of water over the past 50 years:

  • In 1956 the leakage rate was 20%
  • In 2006 the leakage rate was 3.6%

Leakage prevention

The Bureau of Waterworks leads the world in the field of detection and control of leakage with its technology. Compared with other big cities, the leakage rate is maintained at extremely lower rate, despite the extensive length of pipes. Measures include:

  • Underground leakage, the potential leakage quantity is estimated by using minimum night flow measurement, leaks are then detected by using electronic leak detectors.
  • Preventive leakage control, including replacement of pipes and improvement of pipe materials, i.e., from cast iron to ductile cast iron for distribution pipes and from lead to stainless steel for service pipes laid under public roads.
  • Replacement of old pipes with ductile cast iron pipes these have higher strength and better earthquake resistance. It has increased strength because of the addition of magnesium. K-Zero project has been in place since 2002 as a result 98% of the old pipes have been replaced.
  • Monitoring of service pipes - these account for 97% of the total number of leakage repairs so early prevention of leakages is essential.
  • Training and Technical Development Centre - this newly established centre is about improving leakage through research and development.
  • Computerized system - this calculates and gathers whole information on leakages by computer like the causes, details of each repair work, the cost for repairs.

Energy Saving System

The City's Water Supply Operation Centre manages all data relating to water supply through a computerized system which monitors and controls activities 24 hours a day, seven days a week. This ensures that water supply is stable from the purification plants and water supply stations. The system is contributed to the efficient management of both water supply and pump operation.

Water-saving equipment

The City also requests that manufactures develop and supply water saving equipment including, taps, tap plugs, toilets, and washing machines. These are being fitted wherever possible throughout the system. Water-saving plugs were also developed and distributed to customers for free.

Advanced Water Treatment

Advanced water treatment has been adapted to the primal processes of water purification. It is designed to eliminate or reduce trihalomethanes, substances causing chlorine or musty odours, which makes it possible to supply higher quality tap water. The City has also established its own water quality taste objectives. Its Water Quality Management Center obtained ISO/IEC17025 in 2004 - an international accreditation for high standards of water analysis.

CO2 reductions, energy efficiency and financial savings

  • Converted electricity from the volume of prevented water from being wasted (Comparison with the amount of the wasted in 1956) About 167,000 kWh;
  • The electricity charges saved by diminution of leakage rate (Comparison with the electricity charges of 1956) About 2 billion yen (16.7MUSD);
  • Cost for leakage control is about 7.2 billion yen (60.3M USD) annually;
  • Prevented expense by leakage control is about 20.6 billion yen (172.4M USD);
  • The amount of CO2 emissions reduced by diminution of leakage rate is about 73,000 t CO2 (Equal to the amount of carbon dioxide emitted about 31 thousand cars)

Next steps

"Tokyo Waterworks Management Plan 2007" for a medium term and "New Tokyo Waterworks Plan, STEP II" for a long term are to be drafted. The City will implement these plans from synthetic and diverse point of view such as global environmental preservation and contribution to domestic and foreign water industry. Despite the high efficiency leakage rate of 3.6%, the City will continue its efforts to reduce leakage.


Tokyo's model can be applied to other cities. It is highly successful in both reducing CO2 emissions and financially, in making energy savings. Tokyo's measures to control leakage can be adapted to other cities and can play a major role in curtailing CO2 emissions and climate change.