Abstract: A high volume filler and automatic fill-limiting valve unit for customer LP Gas dispensing systems in which tandem backflow check valves are opened by incoming replenishing liquid. When a prescribed outage fill level is reached, the inner one of the valves is released from a mechanical restraint of a float control to convert and operate as an inflow check valve which is closed by the incoming flow pressure drop across it to arrest further inflow and permit the outer one of the valves to also close if it is mechanically free to do so. In either case after inflow shutoff the inner valve under spring pressure resumes its normal outflow check valve position to free the float mechanism and independently supplement the backflow check valve function of the outer valve.