When most of us think of pressure, we’re thinking of gauge pressure. This calculation shows the basis for the conversion factors between depth of water and pressure: 1 foot of water depth = 0.433 psi, or 1 psi = 2.307 feet of water depth. Therefore, the pressure at the bottom of the cube of water is 62.4 pounds / 144 square inches = 0.433 pounds per square inch (psi).īecause pressure acts in all directions, we don’t need an exact shape of a cube to exert 0.433 psi of pressure-any shape or volume of water at a depth of 1 foot will exude 0.433 psi at the bottom, as outlined here. The bottom surface area of that cube of water is 12 inches x 12 inches = 144 square inches. That means if we had a cube of water with a volume of one cubic foot, the water would have a weight of 62.4 pounds. Water has a density of 62.4 pounds per cubic feet. To compute the pressure, we simply need to determine the force (weight) of water acting on a unit of area (one square inch) at the bottom. Imagine that we wanted to know the pressure at a depth of 1 foot under water.
The units of pressure make it easy to conceptualize pressure in a water column. A newton is the unit of force in the metric system similar to how a pound is a unit of force in the English system. In the metric system and SI units, that means newtons per square meter, also known as a Pascal. In the English system, that means units like pounds per square inch (psi). Pressure has units of force per unit of area. Pressure in fluids is a function of the depth of the fluid, the density of the fluid, and acceleration due to gravity. The molecules in a fluid are in constant motion in all directions. The general definition from Wikipedia is the “force applied perpendicular to the surface of an object per unit area over which that force is distributed.” Here is a simple explanation of the general concept of pressure: In fluid mechanics, pressure is exerted in all directions and exists at all points in the fluid, because of the nature of fluids. Simply put, pressure is the amount of force exerted per unit of area. Finally, we’ll conclude with a fun (we hope!) brain teaser.
We’ll also cover some more complicated concepts like absolute pressure, gauge pressure, negative pressure, and vapor pressure. Here we will cover the basic concepts of pressure, including some simple ways to understand pressure and the various units of pressure. We’ll take you on an educational journey to understand water pressure as thoroughly as our pros. But there are some nuances and details about pressure that are important to understand.
1 PSI TO FT OF WATER FULL
Symbols, abbreviations, or full names for units of length,Īrea, mass, pressure, and other types.What is pressure? For those in the water resources field, it’s obvious from everyday work and experience. You can find metric conversion tables for SI units, as wellĪs English units, currency, and other data. Thus a reading of 30 psig on a tire gauge represents an absolute pressure of 44.7 psi.Ĭonversion calculator for all types of measurement units. If a pressure gauge is calibrated to read zero in space, then at sea level on Earth it would read 14.7 psi. Humans do not feel this pressure because internal pressure of liquid in their bodies matches the external pressure. At sea level, Earth's atmosphere actually exerts a pressure of 14.7 psi. By contrast, psia measures pressure relative to a vacuum (such as that in space).
Psig (pound-force per square inch gauge) is a unit of pressure relative to the surrounding atmosphere. You can do the reverse unit conversion fromįoot of head to psig, or enter any two units below: Enter two units to convert From:
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