Carpet cleaner with clear nozzle means that you can see extracted water

https://www.scribd.com/document/1003011853/Allergen-Reducing-Carpet-Cleaning-in-Las-Vegas-Breathe-Easier-at-Home-146710

Carpet purifier with transparent nozzle allows you to see extracted water. Monitor progress and be aware of whilst passes are clear, saving time and keeping off overwetting.