A drip irrigation system is treated about the same way as a sprinkler system. A small drip irrigation zone can be evaluated by placing containers uniformly from front to back in the zone. Typically, catch containers may be placed at the beginning, quarter point, half way, three quarter point and end of each of several laterals. This placement will check the uniformity within the total zone.
For an emitter that drips, a small container can be placed under the dripper or under the line in which the emitter is installed. Be careful so that the discharged water does not run down the drip hose away from the container. Do not raise the line very much to sit on top of the container. For spray stakes, select a catch can that will collect all the discharge water.
Pressure compensating emitters should discharge the same amount of water at all locations if the line pressure is in the normal operating range. Non-pressure compensating drip lines will be subject to the line pressure and will be affected by elevation changes and pressure loss in the lateral lines. More non-uniformity would be expected for the non-pressure compensating emitters.
The type of emitter, operating pressure, length of run and any elevation change are all factors in the outcome. Collect initial data on each of these factors. A pressure gauge at the beginning of the zone would be expected to be in place. If not, install a gauge. Pre-install a gauge at the end of a lateral to determine the drop of pressure in the zone. The difference in pressure readings is the pressure drop.
What kind of drip line is it and what are the details of tube wall thickness, product name, drip emitter spacing, discharge rate and operating pressure. Measure the pressure at both ends of the zone.
Wind speed is usually not a big factor for a drip system but it can affect the spray stakes water distribution and can disturb the catch cans. Record the wind speed before and after the test.
Data Sheet – make a table
Drip line lateral spacing = feet apart
Length of drip line = feet
Type of drip line and emitter:
Emitter spacing on the lateral =
Lateral pressure at heading = psi
Lateral pressure at far end = psi
Expected emitter discharge rate = gph or lph
Make a sketch of the site, showing the irrigation equipment positions, distances, and noting any crop, slope or terrain factors.