Two of the major factors in designing an irrigation system are pressure (psi) and flow rate (Gallons Per Minute, GPM). When you open the hose bibb to water your lawn, the water is already pressurized and comes out at between 5 and 10 GPM. In towns and cities this is part of the municipal infrastructure, but off-grid we must pressurize our own water systems using elevation or a pump - submersible or surface (traditionally coupled with a pressure/bladder tank in a well-house or basement).
Common Irrigation Pressures The relationship between pressure in pounds per square inch (psi) and head (in feet) is especially relevant when sizing pumps for irrigation. Each psi is equivalent to 2.31 feet of head. In other words, if you had a water column that was 231 feet tall, you would have 100psi if you opened a valve at the bottom. Common Household pressure is between 35 and 60 psi. As different types of irrigation require lower pressures, Regulators are used to lower this pressure for calibrated water output. The Total Head for a pump is calculated by adding the height the pump needs to push water and the head needed to create pressure. At right are examples for common irrigation types.
Ensuring Proper Water Volume In addition to the pressure of the water, each different type of irrigation requires certain volumes as well. A large lawn sprinkler needs more water then drip irrigation with a single emitter. When the required flow exceeds the volume supplied, the common practice is to break an irrigation system into multiple Zones so there will still be enough GPM volume for each.
More and more farmers & growers are harnessing the sun to power their irrigation systems then ever before! In 2019 the Engineering team at RPS released two new solar pump systems perfect for irrigation. You now have the ability to 'off-grid' any existing AC well or Jet pump with the RPS WaterSecure™ system or replace your Booster or Shallow Well Jet pump with the adjustable Tankless Pressure™ system.