To fill the G Pen Roam's water tube, first remove the unit's battery and heating chamber by gently pulling up and away from the mouthpiece. The Roam's mouthpiece can then be removed from the enclosed water tube by gently pulling upward. Water can then be poured into the tube's opening until it reaches the black fill line at the bottom of the tube. Once the mouthpiece and battery is reattached, the Roam is ready for use.
