Abstract: A sealing system is provided for a prefabricated pit for servicing an aircraft that is formed with an open bottom and an inner cylindrical wall for surrounding a riser pipe therewithin. An annular rubber boot having annular inner and outer marginal edges is located at the bottom of the pit. The inner peripheral margin of the boot is secured to the riser pipe by a conventional metal band clamp to establish a liquid tight seal therewith, and the outer peripheral margin of the boot is compressed radially outwardly against the cylindrical wall surface by means of an outer clamp.