Hi. Both the flexible and the drain are lead. Running 18 cm is feasible but it will be aesthetically ugly as the pipes will be seen. The water flexible can be extended with Ø1 / 2 "x 30 cm chromed bronze flexible and the drain must be cut about 5 cm before entering the wall, make your mouth as if to insert an accessory of Ø 40 mm and extend it. said, it will work but aesthetically it will not look good.