The water bag should be changed every 30 days for Qufora IrriSedo Cone and Qufora IrriSedo Flow systems (if on Balloon or Klick this should be 15 days) to prevent any mould or moisture occurring inside of the bag.
To prevent this from happening the bag should be hung up out of direct sunlight with the cap/lid open and ensure the purple valve is left open after your irrigation to allow air to flow through the system.