In view of the need to reuse limited water supplies and to ensure the availability of water for use in case of disaster, day-to-day waste water and water from the ponds Sachiga-ike and Sakura-ike in the garden is purified, and used as washing water in restrooms.

Pond water is purified by a new system applying ultraviolet disinfection, ozone oxidative decomposition, and high-density filtration. These ensure the safety of the water and leave no harmful residues to damage ecosystems.