Round Rainwater Tank Dimensions: 1700mm x 1785mm (RD-1700-1785). Kingspan's 4,000 Litre Round AQUAPLATE Steel Water Tank can store water for outdoor use, pool top-ups and use in toilets and laundry. AQUAPLATE is a BlueScope steel specifically designed for use in rainwater tanks and storing drinking water. The corrugated steel tank has an inner poly layer fabricated to a galvanised steel substrate, while the outer layer consists of a COLORBOND laminate coating.