Cavitation is what happens when the pressure inside a pump drops so low that the liquid boils into vapour bubbles, which then collapse violently as they reach higher-pressure regions. Each collapse is a tiny implosion, and together they erode the impeller, wreck efficiency and can destroy a pump in weeks. It sounds like the pump is passing gravel.
Liquid boils not only when it gets hot but also when its pressure falls to its vapour pressure. At the eye of a pump impeller the pressure is at its lowest, so if the suction margin is too small the liquid flashes into vapour bubbles there. As those bubbles move into the higher-pressure parts of the impeller they collapse almost instantly, firing microscopic jets of liquid at the metal surface.
Most cavitation traces back to insufficient NPSH: a suction lift that is too high, a long or clogged suction line, a hot liquid with high vapour pressure, or a blocked strainer. Running a pump far past its best efficiency point makes it worse, because the required NPSH climbs with flow, and pushing a pump out on its curve rather than respecting the affinity laws is a common trigger.
The fix is to restore suction margin: raise the source level or lower the pump, shorten and enlarge the suction pipe, clean the strainer, or cool the liquid. Reducing demand so the pump runs nearer its best efficiency point also helps. Where the duty genuinely needs it, an inducer or a low-NPSH pump is the design answer.
Cavitation announces itself through vibration and acoustics well before the impeller is destroyed, so it is very catchable. A monitoring platform that trends pump vibration and performance turns that early signature into a work order rather than a failure. Fabrico connects to PLCs and IoT sensors on the line, shows the trend on a real-time dashboard, and can trigger a follow-up task when a reading crosses the limit you set. Book a Fabrico demo to see it.
Low flow can cause similar damage. Cavitation usually strikes when a pump runs far to the right of its best efficiency point, but running at low flow rates can set up internal recirculation in the suction or discharge region of the impeller, which causes cavitation-like damage. Before you throttle a pump to cure its noise, check where the duty point actually sits on the curve.
Check the suction line, not just the strainer. Cavitation damage can also come from a pump suction starved by air pockets or by fouled pipes, so look along the suction line for places where air can gather and for scale or deposits narrowing the bore.
Insufficient suction pressure margin, or NPSH, so the liquid boils at the impeller eye. High suction lift, hot liquid, clogged strainers and running far off the best efficiency point are the usual causes.
Like the pump is pumping gravel or marbles, a rattling crackle caused by vapour bubbles collapsing against the impeller.
Low NPSH is the usual cause; cavitation is the result. Cavitation actually starts before NPSH available falls to NPSH required: pump makers publish NPSH required as NPSH3, the suction condition at which cavitation has already cut the pump's head by 3 percent. Keep NPSH available comfortably above NPSH required across the whole flow range; a common design rule is at least 25 percent margin, and more when the pump runs away from its best efficiency point.
Restore suction margin: raise the source level, shorten and widen the suction line, clean strainers, cool the liquid, or reduce flow toward the pump's best efficiency point.
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