Rhode Island Journeyman Plumber Practice Exam

How do you calculate the head pressure for a 6" pipe with 62.5 psi?

1. Capacity multiplied by pipe diameter

2. Capacity divided by the pressure constant

3. Pressure constant times diameter squared

4. Capacity divided by 0.0408 times diameter squared

The correct answer is: Capacity divided by 0.0408 times diameter squared

When calculating head pressure for a pipe, you are generally looking to understand how the pressure expressed in terms of psi translates into height (head) that can lift a fluid. In this context, the formula used often involves a constant that relates pressure to the height of a fluid column and the diameter of the pipe. The appropriate formula to calculate the head pressure in feet, especially for water, is derived from the pressure expressed in psi, taking into account the specific gravity of the fluid (water has a specific gravity of 1). The calculation incorporates a well-known conversion factor, which is approximately 0.433 psi for every foot of head in water. In this instance, the choice that includes "divided by 0.0408 times diameter squared" aligns with how head pressure is commonly calculated, as it accounts for the pressure being converted to head and scales appropriately with the diameter of the pipe. This specific factor of 0.0408 effectively serves to adjust the resulting head calculation suitably for the pressure in psi, factoring in variations that depend on the diameter of the pipe. This method allows us to properly assess how much head is generated by a given psi in a 6” pipe, making it a reliable approach for applications in plumbing and