This paper describes performance solar water heating for flat plate collector. The system of thermal performance designed for dimensions 125 × 110 cm and width 25 cm, in such a way that fluid can flow from inlet to outlet through pipe with longer is 15.9 m, designed as lope square pattern, used the water as fluid flow working with two different flow rate (5.3 and 6.51 L/min). The experiments were carried out under the University of Technology, conditions of Baghdad, Iraq. The result shows that the water at flow rate 5.3 L/min heated more than the flow rate 6.51 L/min, which causes the higher efficiency and effectiveness of the collector, so the maximum temperature was (51.4 °C and 49 °C) at flow rate (5.3 L/min and 6.51 L/min) respectively. The main conclusion is that used this system to heated the water and then used in-house, building and other purposes.