Hot storage tanks (HSTs) have numerous engineering applications, including hot water boilers, hot water storage tanks in residential buildings, hot water storage in solar collector systems, and molten salt storage in concentrated solar power generation systems. The HST performance improves if the tank is thermally stratified. To improve the conditions of thermal stratification of the HST, accomplished by supplying hot water to users in a shorter time, and reducing energy consumption, a chimney-type hot water storage tank (HWST) is proposed. The static mode of this modified type HWST has been previously performed and found highly improve the thermal stratification in the tank. In this paper, the performance of the HWST under dynamic mode is investigated. Two chimney diameters three-inch and two-inch were used under variable flow rates (0.1 to 3 L/min), the usage period was also investigated (10 min and 18 min) to understand the effect of usage time on the performance of the HWST. The experimental data were compared to theoretical results, an accuracy range between 0.9 to 0.96 were achieved and tank efficiency varied from 0.96 at low temperatures to 0.86 at high temperatures. The 2 in chimney produces high top tank temperature in a shorter time, where safe flow rate gradients (positive temperature change) of 1.2 and 1.5 L/min were registered for 18 min and 10 min usage periods respectively.