Japan is piloting a new kind of household water system that could fundamentally change how homes access and reuse water. In several rural and depopulated regions, residents are beginning to rely on compact machines that purify and recycle water inside the home, removing the need for connection to public pipelines.
The shift comes as Japan faces mounting challenges in maintaining its aging water infrastructure. With fewer people living in remote areas, local governments are struggling to justify the rising cost of maintaining long stretches of pipelines. National authorities have increasingly described the current system as financially and logistically unsustainable, particularly outside major cities.
Compact Systems Allow Homes to Operate Without Water Networks
At the centre of this transition is a decentralized water recycling unit developed by Tokyo-based WOTA Corp. Known as the WOTA BOX, the system treats wastewater from showers, sinks and washing machines, purifying it and recirculating it for further household use. The company says the device can recycle up to 97 per cent of domestic wastewater.
The system focuses on greywater, while drinking water and toilet waste are handled separately. Any water lost during daily use is replaced through rainwater, which is filtered within the unit. The entire process is automated and does not require connection to municipal water or sewerage networks, making it suitable for areas where traditional infrastructure is no longer viable.
Company data indicate that the recycled water meets all Japanese tap water quality standards and aligns with World Health Organization benchmarks for safe reuse. After clearing advanced testing stages in 2025, the system entered real-world trials in early 2026.
Rural Municipalities Turn to Decentralized Solutions
Field trials are underway in parts of Akita and Ishikawa prefectures, regions that have seen significant population decline. Local governments there are exploring whether decentralized systems can replace or supplement conventional pipelines that are increasingly expensive to repair and replace.
Government estimates show that replacing a single kilometre of water pipeline can cost up to 200 million yen, with costs rising sharply over the past decade. A 2024 national survey found that a majority of municipalities had postponed essential upgrades to water infrastructure, including earthquake-resilience improvements, due to funding shortages.
Decentralized systems are gaining interest because they can be deployed in stages, reduce long-term maintenance costs and continue functioning during disasters when central pipelines may fail.
Government Policy and Investment Accelerate Adoption
Japan’s central government has formally backed decentralized water infrastructure in its 2025 economic and fiscal reform policy, calling for early implementation to address regional disparities and long-term cost pressures. The policy reflects a broader rethink of infrastructure planning in a country facing demographic decline.
To accelerate adoption, WOTA Corp launched a 10-billion-yen Water 2040 Fund in 2025 to support municipalities with financing, planning tools and deployment simulations. The company’s model allows local authorities to tailor systems based on local needs, separating drinking water, domestic water and toilet water functions.
While the current system still relies on external sources for drinking water, development is underway to fully integrate rainwater purification. The project is supported by national innovation programmes, including NEDO and the Cabinet Office’s SBIR initiative.
Japan’s experiment comes as aging infrastructure and more frequent natural disasters expose weaknesses in centralized systems. After the 2024 Noto Peninsula earthquake, decentralized water units were deployed to restore emergency access, highlighting their potential role in disaster response.
Policy experts say Japan’s approach could serve as a model for other countries facing similar infrastructure strain, offering a hybrid future that combines centralized networks with local, self-sufficient solutions.