1. Total GPM (gallons per minute) __________GPM
How to calculate this: Add up all the emitters in your system or largest zone multiplied by the flow rate of the emitter(s).
What you will need to know: Your watering method, how many gallons per hour you plan to supply to the system at one time (flow rate of each emitter and total number of emitters).
Part 1: Suction Lift __________ft
How to calculate this: This is the vertical distance between water level and pump inlet. (If using a submersible pump this will be zero.)
What you will need to know: What type of pump you will be using. If not a submersible, how many vertical feet are between your pump inlet and the water source?
Part 2: Elevation Change __________ft
How to calculate this: This is the vertical distance between the pump inlet and the highest point in your system.
What you will need to know: How many vertical feet are between the highest emitter/dripper in your system and the pump? See the Water Pump Buying Guide for assistance.
3. Friction Loss (in feet) __________ft
Convert to head in feet using the following equation: PSI x 2.31 = Head in Feet (or Feet of Head).
How to calculate this: For poly tubing, using the Friction Loss Calculator enter your system flow rate in GPH, the size of the poly tubing you will be using, and the total length in feet of tubing you plan to use. Click the calculate button for estimated pressure loss in PSI. For other piping use manufacturers pressure loss charts if available. Here is a link to a PVC pipe pressure loss chart.
What you will need to know: The size and type of your tubing/pipe. Total length of your tubing/pipe.
4. Required PSI (pounds per square inch) converted to head in feet __________ ft
The pressure required by the emitters or watering devices in your system or largest zone. Convert to head in feet using the following equation:
PSI x 2.31 = Head in Feet (or Feet of Head).
How to calculate this: This is the pressure you require to run your system. If you plan to use drip tape, for example, this will require 15 PSI to operate. Whereas, some drippers or sprays may require a higher PSI such as 25, or even 30.
What you will need to know: How much pressure does your watering method require? Will your system have any significant pressure loss?
5. Total Dynamic Head (TDH)__________ft
Add up the feet measurements.
How to calculate this: Add up all the information you have filled out above:
(Suction Lift - ____ft) + (Elevation Change - ____ft) + (Required PSI head in feet ____ ft) = (TDH)____ft
You can now use the GPM and the TDH to map your pump requirements to the manufacturers pump curve performance chart for the closest pump to meet the needs of your irrigation system, water feature or other application.
For a full overview of ALL of the pumps we carry, here is a link to our pump chart: https://dripdepot.freshdesk.com/a/solutions/articles/11000097949