Abstract: Apparatus for checking the presence of liquid at a predetermined level in a container is disclosed. The apparatus comprises valve means disposed externally of such container, manually operable suction means to generate vacuum pressure and connected to the valve means, elongate duct means having constriction means between a first end portion extending into such container to define an opening in the duct means at the predetermined level and a second end portion connected to the valve means, the valve means being actuable by the suction means to close the duct means only on liquid being present at the predetermined level in such container, and indicator means responsive to the closure of the duct means by the valve means to indicate the presence of liquid at the predetermined level in such container.