Emergency Vehicle Technician (EVT) F-3 Practice Exam

Cavitation occurs when the local pressure in the pump (or at the suction) drops below the liquid’s vapor pressure, causing vapor bubbles to form and then collapse as they move through the system. That energy loss disrupts the transfer of water, so you can observe a change in the pump’s performance rather than a straightforward increase in flow. When you RPM up the pump, the pump can develop higher head (more pressure), but if cavitation is present, that energy goes into forming and collapsing vapor pockets instead of pushing more water to the discharge. So you end up with higher pressure without a corresponding increase in water delivered—this is a scenario many technicians associate with cavitation. Classic audible signs like a loud pop in the discharge line can occur, but the underlying performance symptom—pressure rising with little or no gain in flow due to vapor formation—directly reflects how cavitation alters the pump’s head–flow behavior.