Pump problem
Cavitation happens when vapor bubbles form and collapse inside a pump. It often points toward poor inlet conditions, excessive restriction, wrong operating range, or a system asking the pump to do something it should not do.
Plain-English answer
When pressure drops too low inside part of the pump, the liquid can form vapor bubbles. When those bubbles move into a higher-pressure area, they collapse. That collapse can create noise, vibration, pitting, heat, and equipment damage.
A cavitating pump may sound rough, rattly, or like gravel moving through the casing. The sound is a clue, but not every noisy pump is cavitating. Bearings, debris, air, vibration, and water hammer can also make noise.
Clogged strainers, undersized suction pipe, too many fittings, a partly closed valve, excessive suction lift, low source water, high temperature, air leaks, or poor layout can reduce inlet conditions.
The pump needs water to arrive smoothly before it can move water usefully.
Cavitation risk can increase when the pump is forced to operate far from its intended range. The system curve, pump curve, valve positions, filters, and discharge restrictions all affect the actual operating point.
Repeated bubble collapse can pit metal, erode impellers, increase vibration, damage seals, reduce performance, and shorten equipment life.
The earlier the cause is found, the better the chance of avoiding expensive damage.
Prevention may involve cleaning strainers, opening valves, reducing suction restrictions, correcting pipe size or layout, reducing suction lift, maintaining adequate source level, checking air leaks, and selecting a pump suited to the duty point.
| Clue | Possible meaning | What to investigate |
|---|---|---|
| Gravel-like sound | Possible cavitation or severe hydraulic noise. | Suction side, water level, strainer, valves, pump curve. |
| Vibration | Bubbles collapsing, poor hydraulics, or mechanical issue. | Operating point, mounting, bearings, pipe support. |
| Low flow | Restriction, inlet problem, wrong pump, or damaged parts. | Flow rate, filters, suction, impeller, discharge path. |
| Impeller pitting | Possible long-term cavitation damage. | NPSH/inlet conditions, system design, duty point. |
| Air bubbles | May be suction air leak or entrained air, not always cavitation. | Lid seals, fittings, unions, source turbulence, water level. |
| Repeating failures | System problem not solved by replacing the pump. | Pipe design, controls, source, valves, pump selection. |
A new pump installed into the same bad suction conditions may suffer the same fate. Cavitation troubleshooting should look at the full system, not just the damaged part.