A method for filling containers with a liquid filling-medium supplied from a filling-medium tank includes sealing a container against a filling element, connecting an interior of the container to a flow duct within the filling element, adding liquid filling-medium to the container, thereby causing gas to exit the container via the flow duct, using pressurized gas, removing liquid filling-medium from the container through a flow duct, guiding the removed liquid filling-medium to a collection chamber, and monitoring flow of matter that passes through the flow duct on its way to the collection chamber.