A deaerator must be how high above the feed water pump?

• A. Thirty feet
• B. Fifteen feet
• C. Forty feet
• D. Sixty feet

Answer: (A)

The key idea is using the hydrostatic head of a water column to provide adequate suction pressure for the feedwater pump. When the deaerator sits higher than the pump, the water surface inside it creates a positive pressure at the pump suction simply from gravity—the taller the column, the higher the suction head.

With about 30 feet of elevation, you get roughly 13 psi of suction pressure at the pump (since 1 ft of water is about 0.433 psi). That positive head helps prevent cavitation and gives the pump a comfortable margin across operating conditions, ensuring smooth flow from the deaerator to the boiler.

Too little height reduces that suction head and can lead to cavitation or inadequate flow; too much height adds unnecessary structural cost without much extra benefit. Thirty feet strikes a practical balance used in many plants.