The condenser pump is on the first floor and not running. The pressure gauge shows 55 psi. There is 15 feet for each floor. What floor is the cooling tower on?

• A. 6
• B. 12
• C. 8
• D. 3

Answer: (C)

The key idea is that static pressure in a vertical liquid column comes from the height of the liquid above the point you’re measuring. For water, 1 psi corresponds to about 2.31 feet of head.

Convert the gauge pressure to feet of head: 55 psi × 2.31 ft/psi ≈ 127 ft.

If each floor is 15 feet tall, the floor difference is 127 ft ÷ 15 ft/floor ≈ 8.5 floors. The options give whole floors, and 8 floors (120 ft) is the closest to the calculated height, while 9 floors (135 ft) would give a higher pressure (about 58–59 psi). So the cooling tower is on the 8th floor.