Syphonix Auto, for which a patent has been applied, utilises smaller syphon heads than its portable counterpart, as there is no pump on board. A separate electric vacuum pump evacuates a secondary chamber connected by pipework to a maximum of four syphon heads. A sensor in one or more of the heads detects the presence of water and activates the vacuum for just a matter of seconds. This creates a pressure drop in the secondary vacuum unit and the hoses connecting it to the syphon head. Water then flows from the syphon heads across the roof and simply syphons away. Any water entering the pipe back to the vacuum chambers drains out once the pump switches off.