In the last decade, a tremendous effort has been made to find solutions permitting to decrease the consumption of fossil energy. Energy recovery is one of the emerging solutions. It consists in recuperating the waste energy that exists in many systems and reutilizing it in a useful way. Heat recovery from hot water drain is one of energy recovery systems that is taking its reputation nowadays due to the major part of the electric bill occupied by heating domestic water. This paper reports a calculation procedure that can be applied to many drain heat recovery systems. It can be utilized as a pre-calculation tool to evaluate and analyze drain heat recovery systems or as an optimization technique to enhance an existing system. To proceed, a generic experimental setup is devised and a parametric experimental analysis is performed using the developed setup. Experiments have shown that the system can considerably increase the temperature of the cold supply water for some configurations. Based on experimental results, many drain systems can be preliminary evaluated and analyzed using a new suggested systematic calculation procedure based on experimentally determined parameters.