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By Matt Clift (Director of Global Product Management & Marketing)
Choosing the right drip line or tape is essential for ensuring maximum yield and efficiency.
Here are the key considerations to help you make an informed decision for your specific needs.
The first step in selecting the right drip line or tape is identified by the application of use:
The following graph shows a typical flow vs pressure curve of a non-PC drip line.
Simply, the higher the pressure, the higher the flow through that specific dripper.
2 important factors that impact pressure within a drip lateral:
Pressure compensation (PC) drip lines regulate the flow within every dripper so that within a specified pressure envelope, every dripper emits the same flow as shown in the diagram below.
Read more about dripper types, including an explanation of Exponent (X) in the relevant section of Module 2 in the Rivulis Knowledge Hub.
Both AS and ND drippers are PC drippers, being that they both have pressure compensation as a function, but in addition:
In general, a larger internal diameter of a tube allows for longer run lengths. However...
Back to the PC / non-PC discussion, a PC drip line in many cases can allow a smaller diameter tube to be used than a non-PC equivalent. This is because a larger diameter tube is required in non-PC applications to reduce the effects of friction within the tube itself (pressure loss), and the subsequent decrease of flow across the run length. PC drippers, within a wide pressure range, keep the same flow-rate for every dripper, even though the pressure is higher at the start of the tube, and lower at the end.
It is important to keep in mind that larger diameters will require more time for the drip line to fill up at each irrigation event. Larger diameter tubes also generally have a lower maximum pressure tolerance compared to the equivalent wall thickness of smaller diameters.
This is the thickness of the tube itself, and for Rivulis it is generally specified in mil (thousandths of an inch).
Note that some emitters will only work in some wall thicknesses, so your dripper choice will impact what wall thickness range options you can select. e.g. some drippers cannot work in thin (5 - 12 mil) wall thicknesses, and vice-versa. The relevant product brochure will include a table of wall thickness options available for each dripper.
The thicker the wall thickness, the:
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The distance between each drip emitter can be as close as 10 cm (4”) and more than 1 m (40”).
Emitter spacing is a decision based on a combination of the flow-rate of each emitter, the soil type, and the crop planting density.
In general, emitters need to be closer for freer draining soils (see image below).
For germination of seed, and densely planted vegetables, very close spacing (15cm / 6" and below) is recommended. Read our guide for close dripper spacing here.
As the name suggests, this is the volume of water that will pass through the dripper (usually represented as the volume of water per hour).
For non-PC drip lines/tapes, it is important to verify at what pressure the flow-rate is calculated at. As we saw in the previous section, the pressure of the water impacts the flow-rate for non-PC drippers. If a flow-rate is calculated at 0.55 bar (8 psi), it is not an apples vs apples comparison to compare to another product with the same published flow-rate if that flow-rate was calculated at 0.7 bar (10 psi). They are not actually the same flow-rates although the published flow-rate may be the same. Each product table will specify at what pressure the flow-rate is calculated at. Ensure to check this as it can vary between manufacturer, product and region.
Also if your system runs at a different pressure than the pressure used to calculate the flow-rate, your actual flow per dripper will vary according to the pressure you are using.
Furthermore, some product flow-rates are per dripper, others per 100m / 100 ft.
There are many considerations when it comes to flow-rates. We have developed an in-depth overview of flow-rates and product naming that you can view in the Flow Rate section of the Rivulis Knowledge Hub.
Selecting the right drip line / tape involves considering the application type, run length, wall thickness, emitter spacing, diameter, and additional features. By carefully evaluating these factors and choosing the appropriate Rivulis products, you can ensure efficient water distribution, crop health, and system longevity.
For a more detailed dive into product selection, I invite you to explore the full Rivulis Drip Guide series. Visit the Rivulis Knowledge Hub to access a suite of comprehensive resources to optimize your drip irrigation system.
· English: https://www.rivulis.com/knowledge-hub/
· Spanish: https://es.rivulis.com/knowledge-hub/
· Italian: https://it.rivulis.com/knowledge-hub/
Please note. This article is provided as a high level overview only. It is important that you verify what is best for your specific application, including for design, installation, operation, and maintenance. For both personal and irrigation system protection and before use, it is important to read the relevant suppliers’ instructions (for non-Rivulis products such as pumps, chemicals, fertilizers, etc), to consult with applicable professionals, and to read the relevant section of the Rivulis Drip Guide/Knowledge Hub, particularly with respect to safety and handling information, and more detailed instructions for use.
Buying Guide: Driptape, Dripline, or Poly Tubing W/ Emitters
Selecting the proper drip device for your use depends on a couple of variables, each equally important. The three types of products we sell for drip systems are driptape, dripline and blank poly tubing with emitters added as needed. Each is capable of different flow rates and emitter spacings, so it can be adapted to fit many configurations. Preinstalled emitters can be 4”, 6”, 8”, or 12” apart on driptape and 12”, 24”, 36”, or 48” apart on dripline. We do not install emitters on poly tubing, but we do sell them for customers to install.
The first factor that will decide which product to use is the flow rate needed. Knowing how much water your plants need is crucial. This will depend on the overall water needs of your crop or plants, as well as the type of soil they are in. Clay is slow to absorb water and would require a lower flow drip tape, while sand absorbs water quickly, so a higher flow rate is possible. Drip tape will be the lowest flow choice, ranging from a .09GPH emitter to a .27GPH emitter. Dripline is capable of a higher flow rate of .5GPH to 1GPH. Poly tubing can be customized with any compatible emitter. This allows you to tailor the flow and the emitter layout for more custom applications. Self-installed emitter flows can be anywhere from .5GPH to 18GPH. The flow needed will dictate the entire system. Lines and connections need to be sized to accommodate that flow.
The second factor is life span needed. Drip tape has different thicknesses measured in thousandths of an inch or “mil”. The higher the number the thicker the wall of the tape. A thicker tape will last longer than a thinner one. Driptape is best suited to crops that are more seasonal as it is cheaper per foot and most users will discard after one use. The most common thickness is 8mil tape, that is a great starting point for new users. If you get unexpected leaks caused by animals or workers, then trying a thicker tape next year is recommended. If you have success with 8mil then using a thinner tape next season may be possible to save money. If you need a longer lifespan for a crop that grows over multiple years like orchards or vineyards, dripline would be a great alternative to driptape. Dripline is like blank poly tubing, but with pre-installed emitters. Like poly tubing, it can last on average about ten years before any noticeable degradation. For seasonal crops use driptape, for year-round or perennial crops dripline or poly tubing is best.
The third factor is the diameter of tubing. The most common size is 5/8”. It will be easiest to find fittings in this size, whether it is for driptape, dripline, or poly tubing. The reason to go to a larger diameter driptape would be if there is too much pressure loss from row length using 5/8”. A lot of times you can use a lower flow on 5/8” and still have acceptable pressure loss, granted you will need to run the system slightly longer. If you are unable to reduce the flow, then going larger is needed. The next size for driptape is 7/8”. It can have maximum row of ft at .22gpm, whereas the same flow in 5/8” will max out at 835ft. For rows longer than that you may need to use blank poly tubing like ¾" or 1” and install emitters as needed. Use our pressure loss calculator to decide line size needed, based on flow rate and length of run.
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