What is the correct equation for elevation pressure loss or gain?

• A. EP = 2H
• B. EP = H − 0.5
• C. EP = 0.5 × H
• D. EP = 0.25 × H

Answer: (C)

Elevation pressure change depends on how far water must be raised or lowered. A handy field rule is 0.5 psi for every foot of elevation change. That’s what the equation EP = 0.5 × H expresses, with H in feet and EP in psi. If water moves to a higher elevation, the available pressure drops by EP; if it moves down to lower elevation, you gain EP. The other forms don’t match this straightforward per-foot relationship: 2H would imply a much larger per-foot change, H − 0.5 isn’t a consistent head-to-pressure conversion, and 0.25 × H uses the wrong per-foot coefficient.