This work discusses a waste heat recovery system applied to chimneys allowing to heat water in residential buildings. A prototype illustrating the idea is implemented and tested. Different waste heat scenarios by varying the quantity of burned firewood (heat input) are experimented. Temperature measurements are performed at different parts of the heat recovery system. Gas flow rates of the Exhaust pipes of the system are also measured. Using this system, measurements showed that a tank of 95 L of water can be heated up to 78 °C within one hour. Obtained results show that the convection and radiation exchanges at the bottom surface of the tank have a considerable impact on the total heat transfer rate of the water (up to 70%) used in the prototype under test.