A Wave of Water Rate Hikes - The Choice to "Use Rainwater"! "Rainwater Infrastructure" for Water Conservation and Disaster Preparedness

Denka Astec Co., Ltd. (President: Kazuyuki Goto, Headquarters: Minato-ku, Tokyo) proposes a new water infrastructure that utilizes "rainwater" for domestic use amidst rising water rates and aging infrastructure. In Chiba Prefecture, a water rate hike, the first in about 30 years, is planned, expected to affect approximately 3.09 million people. Across Japan, about 96% of water utilities will need to raise their rates by 2046, with an average increase of about 48% anticipated, making the maintenance of water infrastructure a major social issue. Against this backdrop, our company is committed to building a new living infrastructure that achieves both water conservation and disaster preparedness by transforming "discarded rainwater" into a "usable water resource." ＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝ By 2046, Water Rates to Increase by About 1.5 Times. "How to Secure Water" Becomes a Future Social Challenge. ＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝ ■ The Era of Water Rate Hikes Becomes the Norm Water rate hikes are progressing nationwide. The causes are aging water pipes, reduced revenue due to population decline, and increasing renewal costs. The water infrastructure, once considered "cheap and standard," is entering a phase where its very maintenance is becoming difficult. In addition to rising utility and living costs, water rate hikes directly pressure household budgets. Difficulty in maintaining aging infrastructure, an increase in regions unable to renew it, and acceleration of population decline issues. Management uncertainty due to rising water costs and risks to stable supply. ＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝ "Rainwater Utilization" Holds New Potential for Both "Water Conservation" and "Disaster Preparedness" ＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝ Denka Astec proposes a new option: "using rainwater for domestic purposes," leveraging over 70 years of rain gutter manufacturing technology and rainwater collection/drainage techniques. PURE EDEN is the first step, a rainwater tank with a circulation function that can store 100L of clean rainwater. In daily life, it can supplement 20% of household water used for watering plants and flushing toilets. During a disaster, it can be used to flush toilets without electricity. ■ Case Studies of Rainwater Utilization Constructed a system to live solely on rainwater on a remote island (Akashima, Nagasaki) without a water supply. Installed a "rainwater field (catchment area approx. 50㎡)" to collect rainwater, which is then supplied through a storage tank, purification, and IoT monitoring system. ・Water is actually supplied to the "Akashima no Ie" accommodation facility. ・Nearly 100% of the island's domestic water is rainwater (rainwater use is a prerequisite for life). ・A university is supporting the systemization and advancement of the system. <"Konojinagaya" Commercial Facility Rainwater Project, Fukui Prefecture> In the Konojinagaya Rainwater Project, a state-of-the-art rainwater utilization system collects only clean rainwater from the roof into three tanks totaling 3600L. The water quality is enhanced to a potable level and used in a shared kitchen and for toilet flushing. An IoT control system monitors the rainwater volume and allows for remote control. About 200L to 300L of rainwater are constantly used daily for toilet flushing and other purposes. Rainwater is used for watering fields. It can store 2400L and can be monitored remotely. A rainwater tank was installed for toilet flushing in a trailer house prepared for craftsmen commuting from afar for the Noto reconstruction. It can be used repeatedly without electricity when it rains, also serving as a disaster countermeasure. Professor Toshikatsu Kasai Fukui University of Technology, Faculty of Environmental and Food Sciences Professor, Department of Applied Environmental and Food Chemistry, Ph.D. (Engineering) Rainwater utilization, environmental education. Aims to realize a sustainable society through "making it normal to store and use rain." ■ Denka Astec's Proposed "Rainwater Utilization" Solution Our proposed rainwater utilization solution is a "Phase-Free (*1)" "rainwater infrastructure" that provides value in both daily life and disaster situations. 1. Supporting Life Continuity Through Rainwater Utilization Rainwater has high potential as a means of securing domestic water during disasters and can become an effective infrastructure for home evacuation, usable from daily life to disaster times. 2. Improving Toilet Sanitary Conditions During Disasters A system that uses rainwater for toilet flushing has a high potential to improve sanitary conditions and maintains continuity as it can be used repeatedly when it rains. 3. Development Underway to Expand the Use of "Rainwater" for Domestic Purposes Toilets account for 21% of the water required for daily life, and bathing accounts for 40%. In the future, we are developing ways to use "rainwater" not only for toilets but also for laundry and bathing (moving to the next step by the end of fiscal 2026). *1 What is Phase-Free? Phase-Free is a concept advocated by social entrepreneur Yuiyuki Sato in 2014. It is a new disaster preparedness concept that removes the boundary between normal times and emergencies, providing products and services that can be used in either situation. It is gaining attention as an innovative approach that goes beyond traditional disaster preparedness. The essence of Phase-Free is to naturally incorporate elements of disaster preparedness into daily life, rather than as a special action of "preparing." ・Constant Activity: Can be used in any situation. ・Ordinariness: Designed for everyday use. ・Intuitiveness: Easy to understand how to use. ・Inspiration: Design that raises awareness of disasters. ・Popularity: Easy to spread widely. ■ Japan's First (*2) Rainwater Tank for "Toilet Flushing," "PURE EDEN" The first step in Denka Astec's proposed rainwater utilization is the toilet-flushing rainwater tank "PURE EDEN." This product overturns the conventional concept of rainwater tanks being for "watering the garden" and is an innovative product specialized for toilet flushing in both daily and disaster situations. (*2) According to our own research (as of February 2026, for a domestic wall-mounted rainwater tank exclusively for toilet flushing in Japan). 1. Realizes a "Flush Toilet" Usable During Water Outages Without Electricity (*3) In normal times, it is used as eco-friendly toilet flushing water, and during water outages due to disasters, it becomes an infrastructure that can flush the toilet without electricity. One unit can secure 100L (about 20 flushes) of flushing water, and it automatically refills when it rains, boasting a "continuity" not found in stored-water toilets. Furthermore, it is equipped with a unique "water circulation function" to maintain the water quality inside the tank. (*3) Water supply method using height difference (potential energy), such as installing the tank on the second floor and using the toilet on the first floor. 2. Joint Development with Rainwater Utilization Authority, Professor Kasai of Fukui University of Technology Jointly developed with Professor Toshikatsu Kasai, a leading expert in rainwater utilization. It enables the use of rainwater as a safe and sanitary "living resource" based on technical evidence. Together with Professor Kasai, we aim to realize a sustainable society by "making it normal to store and use rain." 3. Wall-Mounted "Functional Beauty" that Blends into Urban Compact Homes Considering Japan's housing situation, we adopted a slim, wall-mounted design that does not take up much space. It is a design that embodies "Phase-Free," enhancing a family's ability to continue their lives without the feeling of "heavy equipment" for disaster preparedness, blending into the everyday scenery. ■ Rainwater Utilization Roadmap "Rainwater Challenge Concept" Starting with "toilets," which account for about 21% of household water use, we aim to realize a world where about 80% of domestic water can be supplied by rainwater in the future. 【Step 1】 Toilet & Watering Use (Current) Popularize the use of rainwater for toilet flushing and watering, centered on "PURE EDEN." 【Step 2】 Expansion to Domestic Water Use (Planned for end of 2026) Develop advanced purification and utilization technology to expand the range of use to about 80% of household water consumption (toilets, baths, laundry). 【Step 3】 "Smart Rainwater Management" with IoT Realize a system that optimally manages and controls rainwater for an entire region by linking real-time weather data with rainwater tanks in each building via IoT. The concept is "each tank is connected by a network, and the entire city becomes a dam," automatically releasing water before heavy rain to free up storage capacity and storing it during droughts. ■ Future Outlook: From "Discarding" to "Utilizing" Rainwater as Social Infrastructure Based on the "rainwater collection and drainage technology" cultivated over many years as a rain gutter manufacturer, Denka Astec is taking on the challenge of building a social infrastructure that circulates rainwater as a precious resource. <3 Social Issues Denka Astec Addresses> Our country faces the urgent need to prepare for massive earthquakes like the Nankai Trough and Tokyo Inland Earthquakes, while also dealing with the worsening damage from heavy rains (inland flooding) due to climate change. We will contribute to improving social resilience based on the following three pillars. ・Countermeasures for Water Shortages: Utilize rainwater as a resource to achieve environmental consideration. ・Preparedness for Disasters: Prepare for disasters with an eye on the Nankai Trough and Tokyo Inland Earthquakes. ・Countermeasures for Inland Flooding from Heavy Rains: Develop products to prevent flooding under floors during heavy rains.