Drip Run Time & How Long to Water

Drip run time is how long your drip system needs to operate each day to replace the water the crop used. A drip system should run just long enough to refill the root zone — running longer pushes water below the roots where it is wasted, and running shorter leaves the crop short. This tool finds that exact duration.

Run time = gross water need ÷ application rate. The gross need is the crop's daily water use (ETc) divided by the system efficiency, expressed as a depth in mm. The application rate is how fast the system wets the ground in mm/hr. Dividing the depth you need by the rate you apply gives the hours (then minutes) to run.

The application rate is the emitter flow times the number of emitters per square metre, converted to a depth per hour. For example, 2 L/hr emitters at 4 emitters/m² apply 8 L/hr/m², which equals 8 mm/hr because one litre per square metre is one millimetre. A denser emitter layout or higher-flow drippers raises the rate and shortens run time.

Once the soil in the root zone is full, any extra water drains below the roots where the crop cannot reach it, carrying nutrients with it. Matching run time to the daily need keeps water and fertiliser in the root zone, saves pumping energy, and avoids waterlogging and leaching.

Use crop evapotranspiration (ETc) from a Pan Evaporation, Reference ET₀ or Crop ET tool for the current stage and weather, in mm/day. Divide by your drip efficiency (about 90%) to get the gross depth to apply. Enter that here and the tool returns the run minutes for your emitter layout.

On light or sandy soils, splitting the daily run into two or three shorter pulses keeps water in the root zone and reduces deep drainage, especially with high application rates. Heavier soils can usually take the full run in one set. The total minutes stay the same — you are just spreading them out.

Yes. Closer emitter spacing means more emitters per square metre, a higher application rate, and a shorter run time for the same depth. Wider spacing lowers the rate and lengthens the run. The tool uses your emitters per m² directly, so changing the layout updates the minutes.

Most drip systems run daily or every other day because drip wets a small soil volume that holds little reserve. Multiply the daily need by the days between irrigations to set the depth per set, but keep intervals short on sandy soils and small root volumes.

They are accurate planning figures, but real emitter flow varies with pressure, temperature and clogging, and ETc shifts with weather and crop stage. Verify with a catch test or soil check, and adjust the daily need as the season changes.