A latent heat storage tank with a helical coil heat exchanger was developed, built, connected to an evacuated tube solar collector, and tested in this study. 25 kg of paraffin wax was used as phase change material (PCM) in the storage tank. During the charging (melting) process, the storage system was evaluated with varied mass flow rates of hot water as a heat transfer medium (5, 8, 9, 10.5 and 13 L/min). The system was also tested with a constant mass flow rate of domestic water during the discharging cycle (solidification). The results also showed that increasing the flow rate from 5 L/min to 13 L/min reduced the charging time from 218 min to 157 min and increased the system's overall efficiency from 28.4 % to 40.5 %.