Abstract: A differential pressure indicator includes an indicator element having a magnet affixed to the lower end thereof, the element being axially movable from a retracted non-indicating position to an extended indicating position. A spring-biased piston made of material which is not a permanent magnet but which is responsive to a magnetic field is axially movable in a fluid pressure chamber in response to changes in differential pressure. An increase in differential pressure causes the indicator element to move upwardly to a visual indicating position where its tip protrudes beyond the casing of the device.