A grain bin vacuum tube extension system with (i) an extension tube comprising a bottom surface and a plurality of slots on the bottom surface of the extension tube, (ii) a sealing strip that is slidably secured to the bottom surface of the extension tube and that comprises a plurality of slots, and (iii) a butterfly valve that is configured to close when the slots on the bottom surface of the extension tube are aligned with the slots in the sealing strip and to open when the slots on the bottom surface of the extension tube are not aligned with the slots in the sealing strip. The sealing strip is slidably secured to the bottom surface of the extension tube such that the slots on the bottom surface of the extension tube align with the slots in the sealing strip when the sealing strip is slid to an open position. The sealing strip creates and airtight seal against the bottom surface of the extension tube when the butterfly valve is in an open position.