The juxtaposed ends of two glass pipe sections are joined by a coupling construction which comprises an inner coupling sleeve having its ends frictionally mounted in coupling chambers formed in cylindrical enlargements (end bells) provided at each of the juxtaposed ends to thereby effect radial fluid seals in the enlargements. An O-ring is disposed in an annular groove formed in the outer surface of the sleeve in the space between the juxtaposed ends to form fluid seals thereat. Threadedly telescoped external coupling rings are mounted over external portions of the enlargements to draw the latter toward each other to effect pressure between the enlargements and the O-ring to maintain the aforementioned fluid seals.