Distribution Tubing For Drip Irrigation
The base of any outdoor or indoor irrigation system is the mainline tubing, also known as distribution tubing.
What is Mainline Tubing
Mainline tubing (a.k.a. supply line tubing or distribution tubing) serves as the water supply for your system. Mainline tubing starts at a water source and is then run as needed. Mainline tubing comes in all different sizes with the most popular sizes being 1/2" drip irrigation tubing and 3/4" irrigation tubing.
Selecting the right size mainline tubing is important. To choose the right size mainline tubing, match your maximum run length and total gallons per hour needed. Once the mainline is laid out in your system, water devices can be inserted directly into the mainline tubing or adapters can be inserted to run micro tubing, drip tape, or dripline away from mainline tubing to the plants to be watered.
What is Micro Tubing
Micro-tubing is commonly used to describe ¼” tubing. Micro drip lines or spaghetti tube is a very small plastic tubing used in drip irrigation systems, generally in vegetable gardens and greenhouses.
Microtubing is inserted straight into the mainline tubing, usually with basic barbed connector fittings. From there you can attach a wide range of emitters or sprayers to emit water to your plants as you see fit.
How do I choose drip irrigation tubing?
To choose the proper tubing for the job, first, you must know what type of tubing you need. Water tubing for drip irrigation can be broken down into three main types: mainline tubing, micro-tubing, and dripline/drip tape tubing. Regardless of the type of tubing selected for your project, there are two bits of information that are necessary when selecting tubing: run length and total flow rate. For example:
- What is the length of the longest tubing run?
- How many gallons per hour will your system be requiring?
Max Run Length For Irrigation Tubing
The maximum run length is the length for which a certain size of tubing can maintain equal pressure. If the maximum run length is surpassed for a specific size of tubing, then the pressure delivered to each dripper or watering apparatus will alter, and this can cause abnormalities such as inconsistent flow between emitters. Maximum run length varies for each size of tubing, so knowing how far you need to run tubing before ordering help to make sure you order the right size for your task.
LENGTH OF RUN LIMITS: ½” drip irrigation tubing can run up to 200 linear ft. ¼ inch tubing should not exceed 19 ft in length.
Maximum Gallons Per Hour (GPH)
When choosing the tubing size for your project, the max run length is important, but the maximum number of gallons per hour (GPH) that specific sizes of tubing can supply needs to be considered as well.
Each size of tubing can only supply a certain number of gallons per hour before too much pressure loss begins to occur. To find the gallons per hour that you need in your system, you simply add up the output of all the watering devices. For example, if your system uses 40 .5-GPH drippers, 20 1-GPH drippers, and 2 adjustable drippers at 10 GPH, the total GPH used is:
- 40 x .5 GPH drippers = 20 GPH
- 20 x 1 GPH drippers = 20 GPH
- 2 x 10 GPH adjustable drippers = 20 GPH
Add the total for each dripper type (20 + 20 + 20) to give a grand total of 60 GPH your emitters will drip.
MAXIMUM FLOW CAPACITY: ½ drip tubing can handle a maximum of 240 GPH or 4 GPM. ¼ tubing can handle a maximum flow of 30 GPH or 0.5 GPM.