Slimline Rainwater Tank Dimensions: 800mm x 2200mm x 1860mm (SL-0800-2200-1860). Kingspan's 3,000 Litre Slimline AQUAPLATE Steel Water Tank with beautifully curved ends can service outdoor gardens, pool top-ups and be plumbed into 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.