Rainwater from the flat roof is filtered through two "Wisy" filters and collected in a 10m3 tank in the building basement.  The harvested water is used for toilet flusing throughout the building, supplemented by mains water.  The building also uses a range of water efficient products and techniques to reduce water demand.  These include low volume dual flush toilets, waterless urinals, percussion taps and awareness training for staff.  Water use is closely monitored and recorded.