Gas Fitter Test 2026 – 400 Free Practice Questions to Pass the Exam

The measurement of 28 inches of water column (W.C.) is a common way to express pressure in gas fitting and HVAC applications. To understand how this relates to other pressure measurements, it is important to convert the 28" W.C. into pounds per square inch (psi).

One inch of water column is approximately equal to 0.0361 psi. Therefore, to convert 28 inches of water column to psi, you multiply:

28 x 0.0361 psi/inch = approximately 1.01 psi

When considering the relationship between pressure measurements, it's essential to differentiate between gauge pressure and absolute pressure. The 1 psi calculated from the conversion signifies gauge pressure, which reflects pressure relative to atmospheric pressure.

Specifically, 28" W.C. translates closely to 1 psi gauge, as it represents the pressure above atmospheric pressure (14.7 psi). Therefore, the correct choice refers to 1 psig, indicating the pressure measured above the atmospheric pressure.

This understanding is critical in gas fitting tasks, as consistent and accurate pressure measurements are vital for safe and effective installations. The other options fail to directly relate to the conversion of 28" W.C. to psi or represent absolute pressure measurements instead.