This bottom nozzle is of the type comprising a perforated plate to allow water to pass through it, the nozzle having lateral faces (24) and at least one anti-debris element (22) positioned on a lateral face (24) to block out debris likely to infiltrate between the bottom nozzle and another adjacent bottom nozzle. According to one aspect of the invention, in the free state, the or each anti-debris element (22) permanently projects from the lateral face (24) on which it is positioned, the or each anti-debris element (22) being elastically deformable so that it can contract towards the lateral face (24) in the event of a force being exerted on the anti-debris element (22) towards the lateral face (24).