3. Water Pressure

Water Pressure Objectives:

• You will learn how to create pressure.
• You will comprehend that pressure is independent of the surface area on which a water column stands.
• You will learn and understand how elevation of a water column affects the pressure at any given point.
• You will understand that water velocity does not create pressure.
• You will appreciate that, for a given flow rate, water velocity is a function of cross-sectional area and pressure is a force causing the water flow through nozzles or hill elevations.


Pressure is a little harder to understand.

Pressure is the force that moves water through a pipe.

We will try to explain it using a water tower and the weight of water. Think of gravitational "head" pressure -- the higher the tower, the greater the pressure. The height of a water tower creates a large elevation difference where the weight of water in a pipe between two elevations creates pressure.

Pressure created by a pump is a little more difficult to visualize.

A pump creates pressure by pushing the water into a closed container (pipe) or a container with limited openings (pipe with sprinkler nozzles or trickle emitters) so it is contained under a force.

Pressure changes in a system by friction losses or by elevation changes.

Pipe size is a factor only in that the water velocity is faster for a given flow rate for smaller pipe diameters . Remember that friction loss is greater for high water velocities.