Which equation expresses static head pressure per foot below the water surface?

• A. Static head X .433 X 3 = firemain pressure required for static head
• B. .444 X every foot below waterline
• C. 0.5 X depth
• D. 1.0 X head

Answer: (B)

Static head pressure is the pressure added by a column of water above a point, and it grows linearly with depth. For seawater, each extra foot of depth contributes about 0.444 psi. So the pressure per foot below the water surface is simply depth in feet times 0.444 psi per foot. That makes the expression using 0.444 multiplied by the number of feet below the waterline the correct one. The other forms either use an inaccurate per-foot factor or mix depth with total head in ways that don’t represent the per-foot pressure increase.