One vertical foot in a riser equals how many psi?

The correct answer is based on the principles of fluid mechanics, particularly hydrostatic pressure. In a vertical column of water, the pressure exerted at the base of the column increases as the height of the column increases. Specifically, for every vertical foot of a water column, the pressure increases by approximately 0.433 psi.

This relationship is derived from the formula for hydrostatic pressure, which states that pressure in a fluid at a certain depth is proportional to the height of the fluid column and the density of the fluid. For water, this means that as you increase the height of the water column by one foot, you will see a corresponding increase in pressure of 0.433 psi. Understanding this relationship is critical for those involved in fire suppression systems and fire alarm systems, as it has direct implications on the design and analysis of piping systems that carry water under pressure.