Class 5 Boiler Practice Exam 2026 - Free Boiler Certification Practice Questions and Study Guide

One psi (pound per square inch) is approximately equal to 28.42 inches of water column. This conversion is based on the principle that pressure measurements can vary depending on the fluid used for measurement.

The water column measurement is derived from the density of water and the gravitational force acting on it. Specifically, 1 psi is defined as the pressure exerted by a force of 1 pound on an area of 1 square inch. When this force is transferred to a column of water, it can be expressed in terms of the height of that column.

Using the formula that relates pressure, density, height, and gravity, we find that atmospheric pressure, which is about 14.7 psi at sea level, corresponds to a column of water approximately 34 feet high, which translates into the conversion factor referenced. It’s an important measurement in boiler operations, as it helps operators gauge the safety and efficiency of their systems based on the pressure within the boiler.

The other options do not accurately represent the conversion from psi to inches of water column based on established hydraulic principles and would not be applicable in this context.