How to Select the Right Tubing for Your Project
To select the right tubing for your project, you first have to know what type of tubing you need. Low pressure tubing, for drip irrigation, can be broken down into three categories: mainline tubing, mircro-tubing, and dripline tubing. Before describing the use of each type of tubing, it is important to first understand the basic rules and limitations of each type. Not adhering to these rules can result in a poorly functioning drip irrigation system.
Regardless of the type of tubing selected for your project, there are two pieces of information that are critical when selecting tubing: run length and total flow rate. For example, what is the length your longest run of tubing needs to be? How many gallons per hour will your system be requiring? To choose the right tubing for your project, both factors need to be considered, but at this moment, let’s look at each separately
Maximum Run Length
Maximum run length is the longest length for which a certain size of tubing can maintain equal pressure. If the maximum run length is exceeded for a size of tubing, then the pressure supplied to each dripper or watering device will vary, and this can cause strange things to happen (e.g., water shooting out of drippers, no water coming out, etc.). Maximum run length varies for each size of tubing, so knowing how far you need to run tubing before ordering helps to make sure you order the right size for your project.
Maximum Gallons Per Hour (GPH)
When selecting the right tubing size for your project, maximum run length is important, but the maximum number of gallons per hour (GPH) that a size 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 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 water 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
Maximum Run Length & Maximum Gallons Per Hour (GPH)
Once you know both of these factors, then it is easy to select the size tubing that best fits your project needs. Take for example, a project that has a maximum run length of 20 feet and a flow requirement of 60 GPH. What tubing could be used? Take a look at this chart:
||Maximum Run Length
||Maximum GPH Supplied
You can see that the run length allows for all sizes of tubing to be used, but because the total GPH needed is 60, this eliminates ¼” tubing because 60 GPH is more than double what ¼” tubing can supply (30 GPH). If ¼” tubing were used for this system, it would not function properly.
Note: If you think you may want to expand your system in the future, it is a good idea to start with one tubing size larger than your run length and gallons per hour supplied require, in order to give you the flexibility to add to your system in the future.
Frequently Asked Questions About Tubing:
- What is Mainline Tubing?
Mainline tubing (a.k.a. supply line tubing) acts as the water supply for your system. Mainline tubing starts at a water source and is then run as needed. Selecting the right size of mainline tubing is important. To choose the right size of mainline tubing, match your maximum run length and total gallons per hour needed with the chart above. 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, 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. It can be used as mainline tubing, but remember that it cannot be over 30 feet in length or supply more than 30 GPH. This works well for small patio areas, but beyond that micro-tubing is often used to take drippers or other watering devices from the mainline tubing to the plant to apply water directly to the root zone. A hole punch is used to create a hole in the mainline tubing (½” or greater) where one end of a connector is inserted; the other is connected to a run of ¼” micro-tubing. Even though the micro-tubing is not being used as mainline tubing, it still can’t stretch more than 30 feet away from the mainline tubing. Micro-tubing comes in either poly or vinyl rolls. Below we’ll briefly describe the pros and cons of each.
- The Differences Between Poly and Vinyl Tubing?
When buying drip irrigation tubing, there is only one size of tubing that requires you to decide between poly or vinyl, and that is ¼” tubing. Vinyl tubing is softer than poly and thus is considered easier to work with. Poly tubing may be a bit stiffer at first, but it does have some benefits. It withstands UV rays very well and does not expand when heated. Many of our customers in the hotter southern states (Texas, Arizona, New Mexico, etc.) have reported that their vinyl tubing began to pop off of the fittings after about 2–3 years of use. Due to the additives to make vinyl tubing softer, it softens much more than poly in the heat of the sun. This can cause the tubing to slip off the fittings after prolonged exposure to sun. Poly micro-tubing is much more resistant to expansion and therefore less likely to come off the fittings or drippers.
- How to Add to Existing Tubing?
Unfortunately, in the drip irrigation industry, there are no industry standards regarding tubing. What this means is that tubing products manufactured by different manufacturers will not necessarily be the same size, even if they both say, for example, half inch (½”). When adding to an existing system, it’s important to know the manufacturer of your tubing as well as the inside and outside diameter of the tubing you want to add to. To find out more about compatibility, check out our compatibility guide.
- What is Dripline Tubing?
Dripline is tubing that has emitters embedded directly into the tubing at preset spacings and dripper ratings. Dripline tubing can save a lot of time, as there is no need to insert drippers. You simply lay out your dripline and connect to your system. Dripline is available in ½” and ¼” tubing sizes with a limited number of standardized emitter spacings and emitter flow rates.
Note: The maximum run lengths for dripline still apply (¼” 30 feet & ½” 200 feet). Below is a chart of available dripline and common uses for each
||Maximum Run Length
||Available Spacing & Emitter Combinations
.5 GPH emitters every 6"
.5 GPH emitters every 9"
.5 GPH emitters every 12"
Note: 6" spacing is recommended if soil is sandy or plants are tightly planted next to one another
.5 GPH emitters every 12"
.5 GPH emitters every 18"
.5 GPH emitters every 24"
1.0 GPH Emitters every 12"
1.0 GPH Emitters every 18"
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