Slimline Rainwater Tank Dimensions: 1150mm x 2400mm x 2020mm (SL-1150-2400-2020). Kingspan's 5,000 Litre "Tall" Slimline AQUAPLATE Steel Water Tank with beautifully curved ends is a popular size for new homes. Ideal for outdoor use, in gardens, pool top-ups and plumbing 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.