Which gauge condition on the suction side indicates a risk of cavitation and should prompt corrective action?

• A. Negative pressure on the suction gauge.
• B. High positive discharge pressure.
• C. Zero pressure.
• D. High positive on the suction.

Answer: (B)

Cavitation happens when the pressure in the suction side falls to or below the liquid’s vapor pressure, forming vapor pockets that collapse as the pump impeller draws flow, causing noise, loss of flow, and potential damage. If the system is showing high positive discharge pressure, it signals that the pump is delivering against a strong head. That heavy load increases the pressure drop the liquid must overcome, which can pull the suction pressure down toward the vapor pressure even though the discharge side is high. In practice, seeing a high discharge pressure on a system can be a more immediate red flag for cavitation risk than other readings because it directly reflects the demanding operating condition that pushes suction pressure toward cavitation-prone levels. Corrective action would focus on reducing the head the pump must develop or increasing the suction available—such as easing discharge restrictions, purging air, or boosting suction pressure—to bring the suction pressure back above the liquid’s vapor pressure.