Slimline Rainwater Tank Dimensions: 850mm x 2000mm x 2020mm (SL-0850-2000-2020). Kingspan's 3,000 Litre "Tall" 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.