Once you no longer try to unscrew the top cap is simply clipped, everything is better. Having set up the charcoal filter carefully rinsed before, you still have to fill the top. I pour a trickle of water for it to be filtered and the filling is provided in full. The amount of water is sufficient for a meal (3).
The filter should be changed when the indicator no longer displays black bars (I confess I do not understand how the system works exactly as it is attached to the cap). To switch it on you must hold the button a few seconds and 5 black graduations appear.