An assembly for an aircraft including a pylon having a lateral wall with a window passing through it, at least one reservoir, each reservoir being in the shape of an elongate ellipsoid with three semi-axes. The dimension of the reservoir along a first semi-axis differs from the dimension of the reservoir along at least one other semi-axis. The reservoir extends parallel to the semi-major axis, between a first end and a second end. The reservoir is equipped with a discharge head at the second end. The reservoir is equipped with a fastening arrangement disposed on the side of the second end and fastening the reservoir to the pylon. The reservoir is positioned through the window with the first end housed in the pylon and the second end outside the pylon.