NFPA 20 Fire Pump Certification Practice Exam

Air entering or trapping in the suction line is the specific risk tied to improper suction piping design. When suction piping has high points, dead legs, or unnecessary length, air can accumulate and form pockets that the pump would otherwise have to lift liquid through. This air reduces the effective pressure at the pump eye, so the liquid can vaporize and cause cavitation. Cavitation disrupts flow, lowers discharge capacity, creates vibration and noise, and can damage the pump impeller and bearings. Because these problems stem directly from how the suction piping is laid out and vented, improper design of that piping is the primary cause of air entrapment.

In contrast, overheating of electrical components is related to motor electrical load and cooling, not the piping layout. Corrosion of suction piping is more about material compatibility and fluid chemistry, not the abrupt piping geometry itself. Increased system efficiency isn’t a risk; it’s more about performance, whereas the real hazard here is losing prime due to air in the suction.