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SESK: Stuff Everyone Should Know · sesk.info/eng-pump-cavitation-vapor-pressure

What initiates cavitation inside a pump?

Local static pressure falls below the liquid's vapor pressure.

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  1. Pressure exceeds critical pressure
  2. Flow becomes perfectly laminar
  3. Pressure drops below vapor pressure ✔

Why: Low pressure makes tiny vapor bubbles form. When they enter higher-pressure regions, they collapse and can erode the impeller and casing.

Huh, didn't know that: The DOE pump sourcebook says cavitation shows up as crackling and popping, like marbles flowing through a pipe.

The dad joke
The pump disliked bubbles because they always burst into the meeting.
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References

Answer: Pressure drops below vapor pressure. Low pressure makes tiny vapor bubbles form. When they enter higher-pressure regions, they collapse and can erode the impeller and casing.

  1. US Department of Energy, Improving Pumping System Performance www1.eere.energy.gov/manufacturing/tech_assistance/pdfs/pump.pdf
    the system pressure is less than the vapor pressure of the fluid, causing the formation and violent collapse of tiny vapor bubbles
    Checked 2026-10-10.

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