Abstract: The roof of floating roof oil tank, exposed to atomsphere, is subject to weather effects.Therefore, central drainage tube is installed for the purpose of immediate draining of the water accumulated on the roof.This paper, detailing current practices of centra)drainage and its existing problems, points out that the rubber hose and foldable tube used over these years have such shortcomings as leakiness, short service life, high maintenance cost.Then, the paper introduces the newly-developed flexible metal hose, which, as substitute of rubber hose or foldable tube, is characterized by moving-free sealing, corrosion resistance, resistance to weathering, and long service life.Described and discussed in detail for the metal hose are its specifications, simulation test outside tank, intank stress analysis and skills on installation.Technical solutions to some possible problems with the metal hose are given so as to make it operate safely and reliably.The possible problems include air lock, 180° dead angle occuring when the pontoon falls to bottom, foreign press on the metal hose, stress at the flange connecting with the hose.