Experimental study on the heat loss from vertical drainage stack, through which some amount of hot water is drained, is conducted in a laboratory. Effects of some factors, such as total volume and flow rate of drained water, pipe length, material of pipe, on the heat loss are investigated. To estimate the heat loss, an analytical model is proposed. It uses the steady falling-film theory and the unsteady thermal conduction equation in pipe wall. It was shown that the heat losses predicted by the simplified analytical model are nearly equal to the experimental ones. A set of numerical experiments using the analytical model is conducted according to design experiment theory. Some significant factors which influence the heat loss are clarified and quantitative effects of each factor on the heat loss are expressed in the form of simple regression equations. These equations are useful to evaluate the energy saving design of drain pipe system. Moreover heat loss from the vertical drainage stack is compared with that from the horizontal drain pipe, which is discussed in the previous paper by the authors. It was shown that the former is greater than the later.