Drip Irrigation Zone Flow Rate Calculator
Add your emitters, set the supply pipe size and pressure, and instantly see whether your water supply can deliver enough flow for every plant in the zone. Nothing uploaded.
Learn more: sizing a drip irrigation zone
Zone demand against supply capacity
Zone flow is the sum of each emitter's rated flow multiplied by how many of that emitter you have. The supply line has its own maximum, taken from a table by pipe diameter: 900 L/h for 13 mm, 2,000 for 19 mm, 3,800 for 25 mm and 6,000 for 32 mm, all at 2 bar.
The maximum scales with the square root of your pressure divided by 2 bar, so the same 19 mm pipe supports about 1,414 L/h at 1 bar. The gauge shows "Near limit" above 70% of that maximum and "Overloaded" above 90%.
How pressure drop behaves
The pressure drop estimate grows in direct proportion to line length. Double the run and you double the loss. It grows faster than flow does, though, because the friction factor depends on how fast the water moves.
For 800 L/h through 13 mm pipe, the calculator gives 0.84 bar over 30 m and 1.68 bar over 60 m. Doubling the flow to 1,600 L/h over 30 m gives 2.83 bar, more than three times as much. Moving the same 800 L/h to 19 mm pipe cuts the 30 m loss to 0.14 bar.
The estimate treats the whole zone flow as passing through the full length. In a real line the flow shrinks as each emitter discharges, so it is a conservative figure.
Runtime from a weekly target
Runtime is the weekly target divided by the number of watering days, divided by the zone flow, converted to minutes. A 50 L/week target over 3 days is 16.7 L per session. At 80 L/h that takes 12.5 minutes.
FAQ
Why does pipe diameter matter so much?
The same flow moves faster through a narrower pipe, and friction rises steeply with speed. That is why the supply table jumps from 900 L/h for 13 mm pipe to 6,000 L/h for 32 mm pipe.
Should I split a large garden into several zones?
Usually, if all the emitters together would push past the "Near limit" mark on the gauge. Zones that run at different times keep each one comfortably inside what the supply can deliver.
What causes uneven watering along a long drip line?
Pressure falls along the line, more so on longer runs and narrower pipe, so emitters further out get less flow. Pressure-compensating emitters are built to hold a steadier flow across a range of pressures, but this calculator does not model them.