The Xiaomi Robot Vacuum X20+ does have an internal water tank, but it is part of the smart all-in-one base station rather than the robot itself. The base station includes a 4L super-large-capacity water tank that supplies water for mopping.

To control the water output for mopping, the system uses the base station to manage the water supply. Here’s how it works:

- The water tank in the base station is filled with water, which is then used for mopping.
- The robot vacuum can adjust the water output based on the selected cleaning mode through the Xiaomi Home/Mi Home app. This allows you to customize the mopping levels (levels 1 to 3) according to your needs.
- The high-speed rotational mopping feature ensures efficient water usage and cleaning performance.

Levels 1-3 control how wet the mops will be when the vacuum leaves the base station