It seems that drip irrigation has become synonymous with "Inline" drip emitter tubing. While today's technology has helped to make most of the product available very efficient, it is imperative that the designer recognizes the correct application. As with any product proper application is just as important as the installation or maintanince for the success of an irrigation system. "Inline" drip tubing is manufactured by inserting a drip emitter directly into the tubing at evenly spaced intervals during the manufacturing process. Usually two holes are then drilled into the tubing at a precise location for every emitter, where the water will drip out. Installations where plants are either very close together or evenly spaced no greater than 3 feet on center, lend themselves perfectly for Inline. Many different brands are readily available, when developing your design it is important to understand the specific product you are using and its hydraulic limits. This information is available from the manufacturer as well as recommended installation practices.
When plant spacings are irregular or greater than 3 feet on center "Online" drip emitters may be the product of choice. Online drip emitter outlets are installed at or near the plants root zone, this helps to eliminate wasteful irrigation between plants. Online emitters are usually punched into the tubing near the plant. This method gives you a little more flexibility. It is equally as important to consider the hydraulic limitations and recommended installation techniques when installing emitters online.
Within a design for example you could have two different scenarios. In one section or zone you might have grouped plants, in this case it may be more efficient to use “online” or point source drip emitters. In another section or zone you may have rowed spaced plants were inline drip emitters might make more sense.
Often times Inline and Online products are perceived to be interchangeable, while both may work for similar applications, it is important to understand the best application for each.