The ball can move up and down. I looked closely, and the ball can seal the hole. I flipped my vacuum upside down and the pressure easily holds the ball there. I suppose it must be there to help the flow. Not sure if any swirling occurs below the impeller suction hole, but I doubt it. Is the sphere acting as a diffuser or nozzle somehow?Just wondering. Thanks.
Shop vacs are designed to suck up liquids and when the tank fills the ball will float and eventually plug the air suction opening to the blower. The ball is there to prevent liquid from the tank from being sprayed out of the vacuum and to protect the motor from that liquid.
