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: zone flow capacity and pressure drop
Why zone overloading causes under-watering
When a drip zone has more emitters than the supply can handle, pressure drops along the line. Emitters at the far end receive less flow than their rated GPH, meaning plants there get less water. This is why one end of your garden looks great and the other struggles despite a working irrigation system. Keeping zone total below 75-80% of supply capacity maintains adequate pressure at the end of the line.
Supply line diameter and pressure
Larger diameter pipes reduce friction loss and can deliver more flow. A typical 13mm (1/2") poly tube at 2 bar pressure can supply approximately 900 litres per hour. Static pressure starts at the tap and decreases along the line due to friction. This calculator estimates maximum flow capacity based on your pipe diameter and pressure, then compares it to your total zone flow.
Flow rate units: GPH vs LPH
GPH (gallons per hour) is the US standard for drip emitter ratings. LPH (litres per hour) is the metric standard. 1 GPH equals 3.79 LPH. The calculator supports both with a unit toggle so you can work in whichever standard your emitters use.
Runtime calculation from weekly target
Divide your target weekly water volume (in litres) by the total zone flow rate to get runtime per session. For a 50L/week zone with 100L/hr flow, run for 0.5 hours per session. Enter your weekly target and the calculator shows the required runtime automatically.
FAQ
How many emitters can I put on one zone?
It depends on your supply line diameter, water pressure, and emitter flow rates. A typical 13mm (1/2") poly tube at 2 bar pressure can supply approximately 900 litres per hour. If your emitters total more than 75-80% of this, pressure at the end of the line drops enough to under-water the plants furthest from the supply.
What is the difference between GPH and LPH?
GPH (gallons per hour) is the US standard for drip emitter ratings. LPH (litres per hour) is the metric standard. 1 GPH equals 3.79 LPH. The calculator supports both with a unit toggle.
How long should I run my drip zone?
Divide your target weekly water volume (in litres) by the total zone flow rate to get runtime in hours. For a 50L/week zone with a 100L/hr flow rate, run for 0.5 hours per session. The calculator does this automatically when you enter a weekly target.