The results of experiments on efflux time during slow draining of Newtonian liquid under gravity from a large cylindrical open storage tank through an exit pipe are presented in this paper. The mathematical equation developed by one of the authors for efflux time for single exit pipe is used to verify the experimental values. The variables studied are dia. of storage tank, dia. of exit pipe, initial height of liquid in the tank. It has been observed that during draining, Froude number remains constant and is independent of initial height of liquid in the tank. Froude number is decreased with increased exit pipe length and is also found to be independent of dia. of storage tank.