Configurable rod for injecting or withdrawing a fluid contained in a tank, this rod being able to inject or to withdraw the fluid at an adjustable level inside the tank, this rod comprising: - an internal tube and an external tube (94; 200), both extending around the same axis of rotation, the external tube surrounding the internal tube, each tube comprising a cylindrical wall impervious to the fluid and separating the inside of the tube from the outside of the tube, - several openings (O i; O ij) distributed along the axis of rotation at various levels N i, each opening (O i; O ij) fluidically connecting the inside of the internal tube to the outside of the external tube so as to inject or withdraw the fluid of the tank, each of these openings (O i; O ij) being created by bringing an internal slot formed in the wall of the internal tube into register with an external slot (F i; F ij; 202) formed in the wall of the external tube, the position of the internal and external slots on the internal and external tubes respectively being such that each opening (O i; O ij) appears only for one respective angular position P i of the internal tube with respect to the external tube, where the suffix i is the order number of the level N i, and - an articulation allowing one of the tubes to be moved in rotation about the axis of rotation with respect to the other in order to move from any angular position P i to any other and different angular position P k, characterized in that the rod also comprises a diffuser (96; 150; 176) facing each opening (O i; O ij) to diffuse the jet of fluid that passes through this opening only in directions perpendicular to the axis of rotation, this diffuser comprising: - a wall (144; 152; 184) situated facing the mouth of this opening (O i; O ij), and - upper (140; 162; 186) and lower (142; 164; 188) plates respectively situated immediately above and below this opening (O i; O ij) and each extending from the external tube as far as, respectively, the upper and lower edges of the wall. - an internal tube and an external tube (94; 200), both extending around the same axis of rotation, the external tube surrounding the internal tube, each tube comprising a cylindrical wall impervious to the fluid and separating the inside of the tube from the outside of the tube, - several openings (O i; O ij) distributed along the axis of rotation at various levels N i, each opening (O i; O ij) fluidically connecting the inside of the internal tube to the outside of the external tube so as to inject or withdraw the fluid of the tank, each of these openings (O i; O ij) being created by bringing an internal slot formed in the wall of the internal tube into register with an external slot (F i; F ij; 202) formed in the wall of the external tube, the position of the internal and external slots on the internal and external tubes respectively being such that each opening (O i; O ij) appears only for one respective angular position P i of the internal tube with respect to the external tube, where the suffix i is the order number of the level N i, and - an articulation allowing one of the tubes to be moved in rotation about the axis of rotation with respect to the other in order to move from any angular position P i to any other and different angular position P k, - a wall (144; 152; 184) situated facing the mouth of this opening (O i; O ij), and - upper (140; 162; 186) and lower (142; 164; 188) plates respectively situated immediately above and below this opening (O i; O ij) and each extending from the external tube as far as, respectively, the upper and lower edges of the wall.