Pump cavitation is the formation and collapse of vapor-filled bubbles when local pressure falls below the pumped liquid's vapor pressure. The bubbles can collapse as they reach a higher-pressure region, damaging pump surfaces and affecting performance. It is a specific fluid-pressure phenomenon, not a name for every noisy or poorly flowing pump.
Pump cavitation is the formation and collapse of vapor-filled bubbles when local pressure falls below the pumped liquid's vapor pressure. The bubbles can collapse as they reach a higher-pressure region, damaging pump surfaces and affecting performance. It is a specific fluid-pressure phenomenon, not a name for every noisy or poorly flowing pump.
Vapor formation differs from air entering a pipe
Grundfos defines cavitation through vapor pressure and the conditions inside the pump. The Department of Energy's pumping-system sourcebook illustrates vapor bubbles forming and collapsing near an impeller and explains the potential for erosion.
Air entering through a leaking suction connection is a separate possible problem. Noise, vibration or reduced delivery can have several causes, so those symptoms alone do not establish cavitation or identify which component needs replacement.
Liquid temperature matters because the relevant vapor pressure depends on the fluid and its temperature. The actual suction condition and operating flow must be evaluated with that information rather than using a noise description as the entire diagnosis.
Suction-head requirements need their stated conditions
Net positive suction head, or NPSH, describes the suction-side head above the liquid's vapor-pressure condition. The available value comes from the actual system; the required value belongs to the identified pump and operating condition. Where pressure readings enter that evaluation, gauge and absolute pressure explains why the reference must be identified.
The Hydraulic Institute's explanation of its updated margin guidance emphasizes manufacturer-supplied information and application-specific evaluation. A listed required value or a simple comparison is not a universal guarantee that no cavitation damage can occur.
Our pump curve entry explains model and operating-point information. Total dynamic head describes a different system requirement. An acceptable discharge-flow calculation does not by itself complete the suction evaluation.
What a useful investigation should record
Give the qualified provider the pump model, fluid, operating temperature, observed symptoms and when they occur. Keep available flow, pressure and service records, including changes to the suction route or upstream equipment. The eccentric reducer entry explains one reducing pattern to identify in those records; it does not prescribe a universal suction arrangement.
Ask which suction conditions and manufacturer limits were evaluated, whether the pump is operating in its permitted range and what evidence supports the proposed cause. A restricted screen, changed fluid condition or unsuitable operating point needs its actual role assessed rather than being assumed from one symptom. If the investigation uses an efficiency curve, best efficiency point explains a different chart term; it does not settle the suction assessment.
Do not throttle valves, change speed or open a pump as a universal home remedy. Any adjustment must respect the identified equipment, cooling, lubrication and system requirements. The broader pump-runs-without-delivery guide covers other causes that remain distinct from this phenomenon.