The apparatus for testing the stability of dispersed particles in flowing suspensions includes a sample receiving cup having a lower wall and an open upper end. A cup outlet is disposed in the lower wall, and the sample receiving cup is adapted for receiving a suspension sample through the open upper end. A pump is in fluid communication with the sample receiving cup through the cup outlet. The pump extracts the suspension sample through the cup outlet to produce a pressurized suspension stream. A recirculation pipe has a pipe inlet and a pipe outlet, the pipe inlet being in fluid communication with the pump for receiving the pressurized suspension stream, and the pipe outlet returns the pressurized suspension stream to the sample receiving cup, through the open upper end thereof. A power monitor is in communication with the pump for monitoring the power output of the pump.