In what units are NPSH values expressed?

• A. Head in units of feed (kPa) (correct)
• B. Seconds
• C. Meters of water
• D. Degrees Celsius

Answer: (A)

Net Positive Suction Head is an energy-like quantity that tells you how much pressure head is available on the pump’s suction. Because it’s a head, its units reflect a height of liquid rather than a time, temperature, or pure mass measure. In practice, NPSH is given as a head unit, such as meters of water, but it can also be represented as a pressure head in kilopascals (kPa) since pressure head and height are directly related by the liquid’s density and gravity. The key idea is that NPSH expresses “how tall of a column” would produce the necessary suction pressure, not a time or temperature. So expressing it as head, including the option using kPa as a pressure-head unit, aligns with how NPSH is defined.