Slimline Rainwater Tank Dimensions: 550mm x 1300mm x 1560mm (SL-0550-1300-1560). Kingspan's 1,000 Litre Slimline AQUAPLATE Steel Water Tank with beautifully curved ends can service small gardens, drinking purposes, or be used as a header tank. This thin tank measures at only 55cm wide so can be easily tucked out of the way. 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.