Uraijit, don't start playing word games with this, it's a waste of time.
When dvan was talking about zero tolerance, he was probably talking about 0 CLEARANCE. Mostly because he didn't realize that the blades had to flex in order to pump water. With a fixed impeller like the engines circulation pump, it couldn't pump water if it wanted to, that is why it's a circulation pump, not a water pressure pump.