Cabinet of Japan Decide to Make Full Use of Rainwater in Newly Constructed Buildings

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On March 10, 2015, the Cabinet of Japan approved the wider usage of rainwater harvesting systems in newly constructed buildings by the state government or incorporated administrative agencies, aiming for a 100% installation rate. The decision was made based on the Act to Advance the Utilization of Rainwater (Rainwater Act, promulgated on April 2, 2014).

This Act aims to effectively utilize water resources by pooling rainwater and using it for various purposes, including toilet flushing, sprinklers and fire suppression, and consequently, to control intensive rainwater runoff into sewage or rivers. Under this goal, the state government and incorporated administrative agencies are required to install a rainwater harvesting system as a general rule, if there is usable space in new buildings to be constructed. Such systems include reservoirs, general service water tanks and grit tanks. The owner of the building (the state or incorporated administrative agencies) can then make use of the rainwater, which is temporally pooled under the lowest floor of the building.

The Minister of Land, Infrastructure, Transport and Tourism also prescribed the Basic Principles to Advance the Utilization of Rainwater on the same day. This includes the significance of promoting rainwater utilization and technical points to be observed, methods for water management to prevent adverse effects on human health, and the roles of the state and local governments in achieving these principles.