Method for installing an elongated element, in a submarine duct, the submarine duct having an entry port and an exit port located in outer liquid (OL) at a second depth,
the method comprising the steps of:




introducing the elongated element into the entry port,
introducing propelling liquid (PL) into the entry port,

characterized in that the method comprises a step of sucking propelling liquid (PL) out of the exit port of the duct with an immerged suction pump being operated at a predetermined suction pressure drop (ΔPpump) of propelling liquid (PL) so that the predetermined suction pressure drop (ΔPpump) applied to propelling liquid (PL) is smaller than a hydrostatic pressure (Phydro) of the outer liquid (OL) at the second depth.