What could cause a pump to show a low suction pressure reading?

• A. Air leaks, a closed intake valve, a clogged strainer, or an insufficient water source.
• B. A leak in discharge line only
• C. Low water temperature
• D. High atmospheric pressure

Answer: (D)

Suction pressure readings on a pump are measured as gauge pressure relative to the surrounding atmosphere, so external air pressure can influence what you read on the suction gauge. If the atmospheric pressure is high, the gauge (which subtracts ambient pressure from the absolute pressure at the suction) can show a lower value even if the actual absolute suction isn’t dramatically reduced. In practice, a lower suction gauge reading can therefore be caused by high atmospheric pressure affecting the gauge indication, not just problems on the suction side.

The other scenarios don’t produce a low suction reading in the same way: a leak in the discharge line mainly affects discharge pressure, not the suction side; low water temperature changes viscosity but doesn’t typically create a low suction gauge reading; and high atmospheric pressure, while it can alter gauge indications, is the factor that would cause a lower reading, making it the best answer in this context. To determine true suction health, consider both gauge readings and the absolute pressure, and verify the water source and any suction-side restrictions.