yeah, I'm not the best at explaining :/
well it sounds more complicated than it really is lol
since SAWD is lighter than soap, it floats on top of the soap. When you turn the engine on, a wall inside the tank will let the soap run into a void, and when the soap runs out, a liquid only wall will stop the SAWD, then a detector near the E-WALL that senses when there's SAWD on the bottom, which then turns off the engine and blocks the on button for the engine
how does the engine work?