Unfortunately, we are currently unable to offer the water tank for the Dreame D9 Max separately, please contact the manufacturer directly: https://ch.dreametech.com/pages....
The hoover uses Wi-Fi to connect to the local network, which is how the application on your phone connects to it. This is necessary for the initial configuration. Thereafter, the wi-fi is no longer required, all you need to do is press a button on the hoover itself to switch it on. If you don't have wi-fi, you might consider models that are less dependent on your phone's applications. The D9 Max is cool though. :)
You can switch it on and then it starts running and systematically vacuums the room or the flat. But it can only be controlled and planned with WiFi GPS and a smartphone. Without WiFi, it's a bit more haphazard... You can only control settings and manage rooms in the app. I was also sceptical, but the app is okay and works great.