In Japan, 15% of municipalities are considering replacing sewers with septic tanks — The Japan Times
About 15% of Japanese municipalities view the possibility of replacing existing sewerage systems with combined septic tanks positively. The results of the survey were published by The Japan Times.
The survey was conducted after amendments to legislation were introduced during the latest parliamentary session. The amendments were adopted to review the policy of expanding sewer networks in view of the costs of maintaining and upgrading outdated equipment.
Survey results
The study covered 1,464 municipalities with populations of fewer than 100,000 people. As of July, 692 municipalities, or 47.3% of the total surveyed, had provided valid responses.
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Of those that responded, 105 municipalities, or about 15.2%, said they were positive about switching to septic tanks. They include the town of Minamiizu in Shizuoka Prefecture, which has already made such a transition.
Costs of aging infrastructure
Sewerage systems in different regions of Japan are aging, and municipalities face the costs of maintaining and upgrading them amid population decline. In January 2025, an underground sewer pipe collapsed in the city of Yashio in Saitama Prefecture, creating a large sinkhole. After that, legislative changes made it easier for municipalities to switch to combined septic tanks by allowing them to reduce or discontinue the operation of sewerage systems.
At the same time, 406 municipalities reported that they currently see no need to replace sewerage systems with septic tanks. Some of them said this could be difficult to implement due to a lack of budget funds and staff.
