Abstract: Disclosed is an assembly including a dump tank disposed near the fill pipe for an underground gasoline storage tank at an automobile service station. The tank is normally isolated by a hand valve and a check valve from communication with the storage tank fill pipe, however, when the storage tank has been filled from a transport vehicle, the gasoline in the fill pipe and the flexible delivery hose may be dumped into the dump tank by opening a manually operated valve. The check valve permits gasoline thus dumped to flow from the dump tank back to the storage tank as gasoline is pumped from the storage tank during normal pump operation of the service station.