Im suprised by this statement, Im no expert on pumps, but I was under the impression that any pump would be under full load, or even excessive load when restricting the output of said pump??? Not being able to efficiently scavange the water would create turbulence at the impeller, forcing the motor to work harder to spin the impeller(motors are wound and loaded to spin at a certain RPM,I believe this is one reason why mag drive pumps dont heat up as much as wound motor pumps do when restricted). At least this was my understanding of basic fluid dynamics and impeller load... Please set me straight if Im under the wrong impression, curiosity strikes!