Defined in DIN 24 260 (September 1986) as: "Formation of vapour from local underranging of the pumped liquid's vaporization pressure and subsequent sudden condensation." One of the effects of cavitation is almost always to cause the pump to run unevenly with strong radial and axial vibrations in the area of the mechanical seal, leading to the following typical types of damage:

• deflection of torque transmission
• wear abrasion on the secondary seal on the shaft side
• tear-outs in the area of the sliding faces as the result of repeated momentary lifting and impacting of the sliding faces, combined with greater, non-uniform leakage

thermal stress cracks and blisters as the result of partial dry running, especially in single-stage pumps with balancing bores in the impeller.