Abstract: A filling device for a storage tank which includes a manifold adapted to connect with a tank inlet on the storage tank, and a storage tank system which includes the storage tank and the filling device. The manifold includes an outer conduit communicating with an interior of the storage tank, an inner conduit communicating with the interior of the storage tank and extending within the outer conduit, a gas outlet communicating with one of the outer conduit and the inner conduit, and a liquid inlet communicating with the other of the outer conduit and the inner conduit. The filling device enables the storage tank to be filled with a liquid through the liquid inlet while simultaneously permitting venting of the storage tank through the gas outlet.