01
About the Utility
The Bureau of Waterworks, Tokyo Metropolitan Government, is the capital’s public water supply enterprise, serving the 23 wards and the Tama municipalities it supplies. Tokyo’s modern system began supplying water from the Yodobashi purification plant in 1898, and the Bureau served a population of 13,928,448 in FY2025. Its direction is set by a long-term strategic vision, within which successive medium-term plans are framed; Management Plan 2026 sets the business and financial plan for FY2026 to FY2028. The Bureau works with its policy collaboration organisation, Tokyo Water Co., Ltd., on overseas projects, and has trained water professionals at the request of Asian cities.
02
Water System
The Bureau purifies and distributes water through an integrated system with a total facility capacity of about 6.84 million cubic metres a day. Distribution reservoirs at purification plants and supply stations hold about 3.33 million cubic metres, a buffer in a city where the Bureau estimates an earthquake directly beneath Tokyo could cause outages across 30-40% of the metropolis. Energy is a defining operating input: the Bureau uses about 800 million kWh of electricity a year, most of it to move water through transmission and distribution, while customer confidence is solid but not universal, with 64.7% of survey respondents satisfied with tap water as drinking water.
03
Infrastructure & Performance
Tokyo’s network is defined by its scale and by decades of leakage control: distribution mains run under public roads across the service area, and replacement of older cast-iron mains with ductile iron was 99.9% complete by the end of FY2025. Leakage, which stood at 15% in 1982, has stayed between 3.1% and 3.9% of distribution volume over the past decade, and most leak repairs now occur on service pipes, but ageing is the rising pressure, as the share of pipes past their legal service life increased to 22.91% in FY2024, while the renewal rate eased below one percent.
Leakage rate
Leakage as a share of annual distribution volume, %, FY2016–FY2025 (fiscal years ending 31 March)
Reported actuals from one published series.
Sources: Bureau of Waterworks, Business Outline 2026, Chapter 3 Section 4 (Leakage Prevention), Figure 3-25.04
Investment & Priorities
Capital spending is climbing. Actual construction and improvement expenditure grew from JPY 111,609 million in FY2021 to JPY 132,373 million in FY2024, with a larger budget for FY2025. Bond issuance has risen alongside it, while the Water Supply Business Account has moved into operating losses. The Facility Development Master Plan sets a ten-year programme for FY2026 to FY2035, and Management Plan 2026 carries resilience, seismic retrofitting and digital efficiency into the coming three years.
05
Sustainability & Resilience
Decarbonisation is a central resilience and cost question, because electricity drives most of the Bureau’s emissions and renewable generation still supplies less than one percent of its electricity use. Its seventh environmental plan, for FY2025 to FY2029, sets 45 specific actions under four basic policies, building on small hydro and cogeneration at purification plants. Seismic resilience runs alongside: supply routes to evacuation centres and major stations were substantially converted to earthquake-resistant joints by the end of FY2022.
06
Key Challenges
- Renewing an ageing pipe network as more pipes pass their legal service life.
- Maintaining supply through a major earthquake directly beneath Tokyo.
- Restoring financial balance as capital spending grows and operating results turn to losses.
- Reducing electricity-driven emissions while renewables remain below one percent of use.
- Holding leakage near historic lows as repairs concentrate on service pipes.