After the cuts of Step 2 are made, we find ourselves in the dirty water tank. There is a Ball Check valve (blue arrows) and the Dirty Tank Full Sensor (red arrow).

The purpose of the Ball Check valve will be covered in the next step.

The Dirty tank Full sensor is just two Stainless Steel wires that extend into the top of the dirty water tank. The wires are separated by a light blue plastic divider that has an opening on the bottom of the tank. Electrons can flow from one wire to the other thru the dirty water once the tank is full.