Irrigation Five Point
Friction Loss Calculator


This calculator is designed to assist you in determining the water pressure [psi] available at various points throughout the irrigation system.
This webpage developed by Garden Galaxy utilizes the Hazen-Williams formula, and is presented as a public service. The page design has been copyrighted in order to assure free access to irrigation planners & irrigation landscapers.
If there any questions regarding its' use or applications please contact F. Rauscher through www.GardenGalaxy.xyz.
Simple designs are easily calculated. Often the images and selection boxes will suffuce for instruction. Less variety in emitter flow rates and secondary supply options add to simplicity. When multiple secondary supply lines are connected to the same primary line; this adds complexity but can be done.


Image [1]
Image-1, above describes the Primary Supply Line "A", a secondary Supply Line "B" leading to the Feeder Section "D". A short ¼" feeder tubing "C" connects the Feeder Section to it's Supply Lines.
This Feeder section can be comprised of one or more drip-emitter lines. If indiviual-autonomous emitters are used these will be connected by secondary ¼" feeder tubing.

Because some irrigation designs can get complex, if the layout your planning has multiple secondary supply lines, a large number of dissimilar feeder sections, or a combined feeder demand over 150 gph; it might be best to REVIEW more detailed instructions.

Image-2, below represents four feeder sections, which (in this example) will be assigned to two different groups. All feeder sections with similar flow demand can be included within the same group.
Lets assmue the three top sections have 22ea 0.65 gph emitters, while the lower section has 15ea 1.0 gph individual emitters.
After selecting the pressure [P1] set by the regulator, the first two rows of boxes would get this input:
[Emitter gph] [Emitter Qty] [Sections in Group]
0.65 22 3
1.0 15 1

After inputting that data, the Calculate-Demand button is pressed.
The input PSI in addtion to the combined Feeder Sections GPH demand will be reported.
If the balance of input data needed is not understood for completing the pressure and flow calculations: it might be best to REVIEW more detailed instructions.

If your irrigation design is complex
or you just want more informastion
on using the Friction Loss Calculator

Image [2]
Determining Section "A" combined "gph"
Estimating demand from all
Feeder sections (like C)

PSI at Valve & Regulator [P1] :

Total Emitter Demand Estimation:

section 1









Supply line "A" Flow & Output PSI

section 2







Supply line "B" Flow & Output PSI

section 3




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