Slimline Rainwater Tank Dimensions: 1150mm x 3500mm x 2020mm (SL-1150-3500-2020). Kingspan's 7,500 Litre Slimline AQUAPLATE Steel Water Tank with beautifully curved ends is a very large slimline. Great for big suburban homes, irrigating gardens and vegetables, and plumbing into toilets, laundry, baths and showers. 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.