Concealed Toilet Cistern Dual Flush WC Hidden Unit Wall Hung WRAS. This WRAS-approved Easi-Plan concealed dual-flush cistern only is designed to be used with back to wall WC toilet pans. The siphon can be set to provide a dual flush of either 6/3 litres (standard), or 4.5/3 litres, and is designed to save on water usage. Having a concealed cistern creates a much nicer aesthetic when compared with exposed, traditional cisterns. Access the cistern easily through the front. Built from strong, durable plastic. Please note: the flush elbow is fixed in place and cannot be moved. The flush pipe can be reduced in length.