Drop tube seal for petroleum underground storage tanks

A unit for storing gasoline comprising:

• a first containment bucket having an open top for receiving gasoline and a bottom having a port;
• an underground storage tank remotely located from the first containment bucket for storing the gasoline, the storage tank having an inlet at the top of the tank;
• a riser pipe extending between the port and the inlet for communicating gasoline between the first containment bucket and the storage tank;
• a fitting disposed along the riser pipe between the storage tank and the first containment bucket, the fitting being coupled to a remote containment bucket;
• a drop tube concentrically disposed within the riser pipe that extends into the storage tank;
• and
• a seal between the riser pipe and the drop tube for containing gasoline vapors, the seal being located below the fitting.

A drop tube sealing assembly comprising:

• a riser tube having a proximal end, the proximal end having internal threads;
• an underground storage tank spaced apart from the proximate end, the storage tank having a threaded inlet;
• a standard pipe nipple having a first end in cooperation with the proximal end, an opposite end in cooperation with the threaded inlet, and an annular inner surface that forms a conduit, the inner surface comprising a female thread section;
• a drop tube adapter fitting concentrically disposed within the pipe nipple, the adapter fitting having an outer surface containing external threads in cooperation with the female thread section;
• a seal disposed between the adapter fitting and the pipe nipple;
• and
• a drop tube having a open end coupled to the adapter fitting.

A method of preventing vapors from passing from an underground storage tank into the atmosphere, the method comprising:

• providing a riser pipe that is connectable and upwardly extends from the top of the underground storage tank into the atmosphere;
• concentrically disposing a drop tube within the riser pipe, wherein the riser pipe extends into the underground storage tank;
• and
• providing a seal between the riser pipe and the drop tube at a location proximate the top of the underground storage tank.