How can I empty the water on a Hoover performa plus?

The simplest way is to lower the drain hose into a dish or bucket to siphon the water away. You need to ensure the hose is as low as possible (you might need to remove the metal clip at the back). Once the water is drained, check the filter (if fitted, it will be at the front behind plastic kick plate, but not on all models).
If no, or very little, water flows the pipe or pump is blocked.

Ron Jaffa
August 2007