Drip irrigation tubing is the polyethylene or vinyl conduit that forms the circulatory system of a low-volume watering setup. It is a highly water-efficient method that delivers moisture directly to the plant root zone, minimizing loss from runoff and evaporation. This specialized piping transports water from the source and serves as the platform for the precise emission devices that regulate flow.
Function and Physical Composition
The primary function of drip tubing is to move water from the source to the precise location of the plant roots under low-pressure conditions. This material is typically manufactured from low-density polyethylene (LDPE) or a flexible vinyl compound. Polyethylene is favored for its durability and resistance to environmental factors, making it suitable for long-term, permanent installations. The addition of UV inhibitors during manufacturing prevents the material from degrading or becoming brittle when exposed to sunlight over many seasons.
Tubing is available in different wall thicknesses, which dictates its intended lifespan and ruggedness. Thicker-walled tubing offers greater durability for permanent systems that remain in place for multiple years. Conversely, thin-wall tubing is designed for annual use, such as in vegetable row crops, where it is removed after a single growing season. The material must be flexible enough to be routed around landscape features without kinking or requiring excessive rigid connection fittings.
Types Based on Water Delivery
The two main functional categories of drip tubing are distinguished by their role in water release. Supply or blank tubing is used exclusively for water transport and does not contain any built-in emission points. This type acts as the mainline or sub-main, requiring a user to manually punch holes to insert external emitters, sprayers, or micro-tubing. This allows for maximum customization of water delivery points.
In contrast, emitter tubing, also called drip line, has emitters pre-installed at set, uniform intervals, such as every 12 or 18 inches. This design is an efficient choice for watering linear plantings like vegetable rows or hedges with consistent spacing. Many high-quality emitter lines feature pressure-compensating emitters. These internal mechanisms regulate the water flow rate, ensuring the first emitter delivers the same amount of water as the last one, even across varying terrain or long run lengths.
Sizing and Pressure Considerations
Tubing diameter is a practical consideration because it directly influences the volume of water the line can carry and the maximum length of a run. Mainline tubing typically comes in 1/2-inch or 5/8-inch diameters, allowing it to transport a greater flow rate, often up to 240 gallons per hour for the 1/2-inch size. Exceeding the maximum flow rate or run length results in excessive pressure loss and uneven watering.
Smaller 1/4-inch micro-tubing, sometimes called spaghetti tubing, branches off the mainline to feed individual plants or containers. This smaller diameter handles low flow rates and short runs, usually under 30 feet. Drip tubing systems operate optimally at low pressures, generally between 20 and 40 pounds per square inch (PSI). Since most household water sources operate at a much higher pressure, a pressure regulator must be installed to protect the tubing and ensure emission devices function correctly.