Pressure loss due to elevation, also known as head pressure, is calculated based on the vertical change in height and the specific weight of water. The change in elevation is the final height minus the initial height (15 ft - 6 ft = 9 ft). A one-foot column of water exerts a pressure of 0.433 pounds per square inch (psi). To find the total pressure loss, multiply the change in elevation by this constant.

Calculation: 9 ft × 0.433 psi/ft = 3.897 psi.

This represents the additional pressure the system must overcome to lift the water 9 vertical feet.

A. 3.6 psi (2.4804 bar) is incorrect. This value would result from an incorrect elevation change of approximately 8.3 feet, not the 9 feet specified.

C. 4.050 psi (2.6850 bar) is incorrect. This value would correspond to an elevation change of approximately 9.35 feet, which is not the case here.

D. 4.5 psi (3.1005 bar) is incorrect. This value would result from an incorrect elevation change of approximately 10.4 feet.

1. NFPA 13, Standard for the Installation of Sprinkler Systems Handbook, 2022 Edition. Chapter 29, Hydraulic Calculation Procedures, Section 29.2.2.1, "Elevation Pressure." The handbook commentary states, "A pressure of 0.433 psi (0.03 bar) is exerted for each foot (0.3 m) of elevation." The calculation is a direct application of this principle.

2. NFPA, Fire Protection Handbook, 21st Edition. Volume 2, Section 16, Chapter 2, "Hydraulics for Fire Protection," page 16-22. The text explains the components of the Bernoulli equation, including the potential energy term due to elevation (z). It explicitly uses the conversion factor where 1 ft of water head is equivalent to 0.433 psi.

3. Oklahoma State University, College of Engineering, Architecture and Technology. Course: FST 3333 - Fire Protection Hydraulics and Water Supply. Course materials on "Principles of Hydraulics" specify the formula for calculating pressure due to elevation (static head) as Pe = 0.433 × h, where 'Pe' is elevation pressure in psi and 'h' is the height in feet.