A drainback system works on the "drain back" principle. When inclement weather or nightfall shuts down the system, the water in the solar-collector loop drains back into an indoor fluid reservoir by the force of gravity.he water is pumped into the collector piping whenever the system is reactivated.

Heat energy is not wasted in heating the solar collector (as in recirculating systems). Cycling on partly cloudy days does not dump energy (as in draindown systems) since the collector fluid is stored in an insulated reservoir. Drainback removes all water from the solar collector and piping whenever the solar energy collection process is not active. Freeze protection is automatic and fail-safe.The main components of the RADCO Drainback System are a water storage tank, a smaller tank that stores heat-transfer fluid (usually water), a solar panel collector that captures heat from the Sun, and a heat transfer system that transfers heat to the water tank.