Sewerage Day

What Is Sewerage Day?

September 10th is "Sewerage Day" (Gesuidō no Hi) in Japan. It began in 1961, when the Ministry of Construction (now the Ministry of Land, Infrastructure, Transport and Tourism) established "National Sewerage Promotion Day," and in 2001 it was renamed "Sewerage Day" to give it a friendlier name. The day calls for broad public understanding and cooperation with the role of sewer systems, to help advance their development.

Why September 10th?

The date is linked to "Nihyakuhatsuka," a seasonal marker falling around the 220th day counted from Risshun (the start of spring). Because it falls in the typhoon season, it was considered a fitting time to highlight one of the sewer system's key roles: draining rainwater and preventing flooding in towns and cities.

• Established in 1961: at the time, only about 6% of the population was served by sewers, and "National Sewerage Promotion Day" was launched to spread sewers nationwide.
• Renamed in 2001: more than 100 years after the original Sewerage Act of 1900, and with coverage having passed 60%, the day was renamed "Sewerage Day."
• The surrounding week: a variety of events promoting sewerage services are held across Japan around this date.

What Do Sewers Do?

Sewers are vital infrastructure that safely handle household wastewater and rainwater, protecting the hygiene and safety of our towns.

• Wastewater treatment: purifying sewage from homes and factories to protect the environment.
• Rainwater drainage: helping prevent flooding during heavy rain.
• Public health: contributing to the prevention of infectious diseases and better living conditions.

The Technology Behind Sewers

Advanced technology is at work in places we never see.

• Sewage treatment plants: microorganisms are used to purify wastewater.
• Rainwater storage facilities: temporarily holding water during downpours to prevent flooding.
• Combined and separate systems: some systems carry sewage and rainwater together, while others keep them apart.

Interesting Facts About Sewerage Day

• Sewer coverage in Japan: as of the end of March 2025, 81.8% of the population lived in areas served by sewers. Coverage is high in cities, but large regional differences remain a challenge.
• The start of modern sewers: when the original Sewerage Act was enacted in the Meiji era, outbreaks of cholera and other infectious diseases were frequent, and improving public health was a major goal.
• Manhole cover culture: Japan's local designer manhole covers are popular with collectors.
• Advances in flood control: giant underground storage facilities, such as the Metropolitan Area Outer Underground Discharge Channel, have been built.
• Reusing wastewater: efforts are also under way to reuse treated water for industrial and agricultural purposes.

Ideas for Sewerage Day

• Look up how the sewer system works where you live.
• Hunt for designer manhole covers or manhole cards.
• Check evacuation information and flood risks for heavy rain in your area.
• Use water carefully and aim for a lifestyle with less environmental impact.

Unseen Infrastructure Supports Our Everyday Peace of Mind

September 10th's "Sewerage Day" is a day to turn our attention to the sewers we rarely think about. They protect our towns, our environment, and our daily lives. Take a moment to appreciate them and to think about the water environment around you.