Abstract: A tankless return hot water return system to facilitate whole-house or whole-building hot water return recirculation used in conjunction with tankless water heaters. The system is designed to compensate for tankless head losses and to protect the tankless heat exchanger. The system has a hot water return by-pass for heat exchanger protection. The invention utilizes the tankless water heater as the heating source for the hot water return and eliminates the need and use of tank-type water heaters for tankless hot water return recirculation. The system is self-contained with built-in temperature sensing and does not require any auxiliary controls, sensors, switches, timing mechanisms or remote activation. The system is energy efficient and water conservative.