You may have encountered the message on your Alde control panel telling you that the air cushion needs to be replenished or renewed. 

If you are traveling, emptying & filling your water system regularly, you may not see this message often as this helps let air into the system naturally. 

You'll want to turn off your water pump and open a hot water tap to allow the plumbing lines to de-pressurize.

Open the yellow safety drain on the floor near the main Alde unit for 10 seconds or so.

(The Alde is typically located under the bed or dinette area)

After 10 seconds, close the yellow valve once more. 

You can now close the hot water tap that you opened in the earlier step (and re-enable the water pump switch if you wish)

Here is a video from Alde on how to perform this task: