Solar Water Heater (SWH) is a water heater that relies on solar thermal energy to heat the water. SWH requires Thermal Energy Storage (TES) to store heat energy from the sun. Water is a Sensible Heat Storage (SHS) type. Water has the advantage of being easily available, inexpensive and high conductivity value. Much research has been done on SWH with water as a heat sink, but not much has been discussed about the rate of heat release that occurs in SWH tanks. The purpose of this study was to determine the evolution of the water temperature in the SWH tank, the rate of release of water heat, the rate of decrease in water temperature and the time needed during the process. The study was discharging discontinuous carried out by flowing water into the tank gradually, that is by flowing every 5 minutes after which it was stopped for 5 minutes with variations of discharge 1; 1,5; 2; 2,5 LPM from the initial temperature of around 70℃ in tanks up to 35℃ temperature in the reservoir. Data taken during the research are temperature data for each thermocouple point installed. From the results of the study, it was found that the evolution of the temperature of the water gradually decreased and wavy temperature, so that the longest temperature drop in the middle vertical row thermocouple and the fastest decrease in temperature on the horizontal line thermocouple. The greater the variation of the water discharge, the faster the heat release rate and the time needed for the process. The biggest value of heat release rate is 1007,30 J/s, the biggest decrease in water temperature is 17,53 ℃/hour and the fastest time needed is 1 hour 47 minutes 5 seconds.