Micro-tubing refers to the small ⅛” and ¼” polyethylene (PE) and vinyl (flexible PVC) tubing used in drip irrigation as feeder lines from the distribution or main lines to plants. It makes setting up a drip system much easier than trying to run your larger tubing close to each plant.
In rare circumstances, micro-tubing can be used as the main distribution line for low flow systems less than 30 feet from the water source to the farthest plant you are watering. The longer the tubing run, the more friction loss you will incur. Friction loss is the loss of pressure due to the movement of the fluid against the inner wall of the tubing. Additionally, any fittings or drip emitters installed in the tubing will increase this friction loss because of the turbulence they create when the fluid contacts the change of surfaces.
Why is this so important? Drip irrigation is a low flow, low pressure type of irrigation meant to put small amounts of water right where the plants need it. The maximum recommended operating pressure of the micro-tubing is probably 30 - 35 PSI, with 15 - 25 PSI being the most common. Plus, each size of tubing has a maximum flow rate for optimal operation. So you can see, by the chart below, that losing pressure in a long run of tubing can affect the flow in an excessive length, and the drip emitters won’t operate as well or, in some cases, at all. If you must use maximum flow with micro-tubing it is often better to keep run lengths shorter.
As an example, we list the max capacity of our ¼” (.170” x .250”) tubing at 30 feet and 30 GPH, but if you were to need 30 foot runs you may experience high pressure loss if trying to operate at or near maximum flow rate. This situation could be resolved by using two 15 foot runs instead of one 30 foot run.
Micro-Tubing Friction Loss Chart
Friction Loss in PSI/100 ft
It is not recommended to use the ⅛” tubing as distribution lines servicing multiple drip emitters. This is mainly used for feed lines to or from drippers or to spray stakes, individually. Examples include the two and four way dripper manifolds with drip arrow sticks or the Primerus Spot Spitters, see images below. Both of theses items are frequently used in nursery and greenhouse applications.
Micro dripline is another popular item used in home gardens. The same basic principles apply to its use as solid micro-tubing. We recommend the same capacity limitations to ensure the best and most uniform operation of micro dripline with built-in emitters. Our ¼” dripline has 0.5 GPH emitters installed at selected spacings. The ¼” dripline is easy to work with. Most folks find it even more economical once they realize the time savings, too. We recommend it in flowerbeds, landscaped areas with non-uniform plantings, and raised garden beds. Standard spacing is 12” as most emitters can provide coverage for a one square foot area. The closer spacings of 6” and 9” are often the choice for gardens or raised beds with tightly spaced vegetables or quick-draining soil mediums for better coverage. In the graphic below, you can see how using dripline for things like carrots or spinach that are planted closer together is beneficial, while others like cabbage or tomatoes might better utilize individual drippers near each plant.
Here are a few other resources you may find helpful: