From potted herbs to huge vegetable patches, drip irrigation can be a great way of watering – but you’ll need to know what type of irrigation emitter to use. There are plenty of different types and sizes of emitter, and each one has its own purpose. So what is a drip irrigation system, what are drip irrigation emitters and when should I use them?
Drip irrigation emitters are the attachment to your drip irrigation system that regulates a consistent flow of water. The emitters force water out at a much slower rate than your tap does, ensuring your plants don’t get over watered. Without emitters, your irrigation system would run like a tap.
So you know that your plants benefit from a drip irrigation system, but you have no idea how to set up your system. Don’t worry! In this article, we’re going to cover everything you need to know about drip irrigation emitters, from how they work to how to install them.
Read on to learn all about emitters for your drip irrigation system.
Table of Contents
What Are Drip Irrigation Emitters?
Drip Irrigation Emitters, or ‘drippers’ are devices that are used to control the volume and flow rate of water from the tubing to the plants. These devices are essential as without them, plants with low water requirements could drown or suffer root damage, and soil can become waterlogged.
Drip irrigation drippers are generally spaced more than one metre apart, in which one to two emitters are used for a single plant. But closely spaced emitters are used for row crops to better wet a strip of soil. Although there have been a number of different emitter designs, the basis remains the same — an emitter which is able to provide a specified and constant discharge of water that is not very susceptible to pressure changes, and does not easily block.
It is important to know that Drip Irrigation Emitters cannot operate by themselves, and are only a part of a Drip System Layout. This setup includes the following:
- Pump Unit – Takes water from the source and provides the necessary pressure for delivery into the pipe system. This may also include a pressure regulator.
- Control Head – Consists of valves that control the release of water and its pressure in the entire system. It could also have an irrigation filter to clear the water, or a fertiliser or nutrient injector.
- Mainlines, Submains, and Laterals – These supply water from the control head into the fields, and are usually made from PVC, polyethylene hose, and are usually buried below ground.
Types of Drip Irrigation Emitters
The two primary types of drip irrigation emitters are On-line Drippers, and Inline Drippers. On-line drippers are mounted on top of lateral pipes, while inline drippers are emitters that are part of the laterals themselves.
On-line Drippers
On-line drippers are mounted on top of lateral pipes, and are usually used for groves and orchards where the amount of drippers, its spacing, and location are designated during the installation and adjusted accordingly throughout the years of growth by the grower.
They are also used in watering crops placed in pots and containers in nurseries, and as well as for landscaping.
These drippers allow the use of split outlets and other flexible applications according to the requirements of the crops. They are typically installed on top of LDPE pipes, and are commonly installed using a manual punch. They usually come in sizes between twelve and twenty-two millimetres in diameter. As previously stated, these can be used in flexible applications and as such, can accommodate micro accessories and flow-equalisers.
- Long-Path Emitters – These types of emitters have long water paths which circle around a barrel-shaped core. These are usually large in size because of the need to fit the long tube in.
- Short-Path Emitters – Similar to the Long-Path Emitters but with a shorter and smaller water path. These are cheap and will work on very low-pressure systems such as gravity flow drip systems fed by water from rainwater harvesting. Their primary disadvantage is that they easily clog especially if the water has a lot of minerals in it. These also have poor water distribution uniformity compared to other types.
These are best used on small systems in which water distribution uniformity is not critical but cost efficiency is. The most common subtype under this is called the ‘Flag Emitter’, or a ‘Take-apart Emitter’.
- Turbulent-Flow Emitters – Also known as sealed turbulent flow path dripper, is a cost effective type of irrigation dripper that excels at controlled watering for both large scale horticulture and home irrigation.
- Vortex Emitters – With this type of emitter, water runs through a vortex (whirlpool) to reduce the rate of flow and pressure. By swirling the water around the outlet hole water pressure and rate of flow drops. Most vortex emitters are equipped with small inlet and outlet holes. Unfortunately, due to the small holes water can easily clog up.
- Diaphragm Emitters – These types of emitters use a type of flexible diaphragm to reduce the water’s rate of flow and pressure. Some have diaphragms with holes that stretch, while others move the diaphragms back and forth to reduce the size of water passages. Keep in mind that since they have moving parts, they will eventually wear out. However, they are much more accurate in controlling the water’s flow and pressure.
- Adjustable Flow Emitters – As its name suggests, these have an adjustable flow rate. These emitters generally have a dial that can be turned to change the rate of flow. They are designed similar to Short-Path Emitters, and are usually only recommended for plants in pots or hanging baskets. These also allow a much higher rate of flow than other emitter types, which could prove to be useful if you only need a few on a valve circuit.
Inline Drippers
Also called ‘driplines’, inline drippers are drippers that form an integral part of the dripping laterals themselves. They create smooth and bump-less ducts that allow quick and easy deployment and collection of the driplines. They are used primarily in field crops, greenhouses, dense orchards, citrus groves, underground irrigation, and even in ornamental applications. These drippers are factory-fabricated with specific flow-rates and intervals. Inline drippers can be sourced at all home irrigation suppliers.
Types of Inline Drippers:
For those who use inline drippers, it is customary to use three types of duct drip laterals:
- Low Density Polyethylene Piping (LDPE) – LDPE pipe is considered to be the most professional and most expensive lateral. These are assembled parallel within the pipe manufacturing process, whose drippers are usually cylindrically shaped and are concealed inside the drip lines.
- Flat LDPE – Tubings that are produced in an oval, flat, cross-section shape to save space during transport and storage. Drippers are installed parallel to the pipe within the manufacturing process, whose drippers are relatively flat with a small profile to minimise disorders in the flow in the drip lateral.
- Drip Tape – Generally used for field crops and seasonal crops on a large scale. They can also be used when the grower prefers to throw or recycle after every season, rather than scrolling and reusing. These are also used in underground drip lines for seasonal row crops.
What Do The Colours Mean on Drip Emitters?
The colour coding on drip emitters represents their water outputs, and the flow rate of water the dripper will emit under different kPa conditions. 2 lph is red, 4 lph is black and 8lph is green.
Although drip emitters have designated flow rates (also known as the nominal flow rate), these can be adjusted accordingly by changing the pressure in your drip irrigation system.
See the drip irrigation colour code table below:
| COLOUR | Red | Black | Green |
| Water Flow Pressure (kPa) | 2lph unit | 4 lph unit | 8 lph unit |
| 50 kPa | 1.4 | 3.0 | 6.0 |
| 75 kPa | 1.7 | 3.6 | 7.4 |
| 100 kPa | 2.0 | 4.1 | 8.4 |
| 125 kpa | 2.2 | 5.0 | 10.2 |
| 150 kPa | 2.4 | 5.0 | 10.2 |
How Do You Size Drip Emitters?
Plants requiring a higher flow rate need red drippers, while black drippers are best for those requiring a much weaker flow rate. Drip emitters are coloured to indicate the flow rate they will produce, so you can choose the correct one based on the type of plants you are watering, and how much flow rate they require.
There are a lot of factors to consider when choosing the right flow rates — crop type, emitter spacing, crop spacing, drip tubing length, irrigation area elevation, and soil type, among others. You can use a water flow meter to formally test your flow rate.
Note that there is a difference between water pressure and flow rate – it’s important to consider both variables when choosing the right drip emitters.
Keep in mind that mixing emitters with different flow rates in one drip irrigation system is not advisable. Carefully select one flow rate and use it for the entire system. The only time mixed flow rates are advisable is with potted plants, since these come in different sizes of pots and different types of soil.
Choosing the Right Drip Irrigation Emitter
If your plants need minimal flow rate, then a black labelled inline drip irrigation emitter is going to be the best choice. This is because black colour coded drippers will drastically reduce the flow rate of water coming from your tap, and give your plants the most gentle watering possible.
However, the type of dripper you choose will ultimately depend on the type of plants you have. Some drip watered plants need a higher flow rate of water, and so a higher rated dripper may be better. Even the type of soil can affect the type of dripper you install, as water is absorbed at different rates in different types of soil.
As such, it is best to consult your drip irrigation supplier to ensure that you buy the right emitter for your intended purpose.
Pressure Compensating vs Non-pressure Compensating Emitters
Drip emitters have two categories: Pressure Compensating and Non-pressure Compensating. However, their names can be misleading, as all emitters are capable of pressure compensation to varying degrees.
- Pressure Compensating Emitters – Designed to discharge water at a uniform rate under a wide range of water pressures. True pressure compensating emitters give the same flow at 3.0 bars (45 psi), as they do at 1.0 bars (15 psi). Most emitters that fit this specification are diaphragm-type emitters, with some exceptions.
- Non-compensating Emitters – Unlike pressure compensating emitters, these are unable to keep a uniform rate when the water pressure is changed drastically. These emitters also generally do not have rubber diaphragms.
Since all manufacturers can simply label their emitter as ‘pressure compensating’, the only real way to identify whether an emitter is truly pressure compensating is to either test it, or carefully cut it open for examination. However, keep in mind that most people will not have to use pressure compensating emitters. These are usually very expensive and are not cost-efficient for most residential applications, or small scale agricultural work.
Pressure compensating emitters become important when you have an elevation difference of more than one and a half metres in the irrigation area.These kinds of emitters should also be used when you have plans on stretching the limits of your irrigation setup, such as utilising a drip tube longer than what is recommended.
You should also consider the benefits of a pressure regulator for your drip irrigation system.
How Many Emitters Can I Put on a Drip Line?
Emitters should be installed roughly a metre apart on a drip line, and a plant normally needs no more than two emitters watering it. If you have more than one emitter per metre, you may find your system has water pressure issues, and can develop clogs more easily.
Having two emitters for one plant also means there is a backup if one ever clogs up (which actually happens occasionally even on the best designed and maintained drip irrigation systems). The type of emitter and how close you put them will also depend on the thickness of the irrigation piping. Assuming you are using a 2lph flow rate emitter, the spacing for a 13mm thickness tube would be as follows:
| Water Pressure | Minimum Emitter Spacing | Maximum Emitter Spacing |
| 150 kPa | 50cm | 66cm |
| 200 kPa | 64 | 85 |
| 250 | 74 | 98 |
| 300 | 74* | 98* |
| 350 | 74* | 98* |
*Spacing capped due to potential issues with flushing. If multiple lateral flush valves are installed, the distance between emitter spacings can be greater.
Related Questions
Can You Add Emitters to Emitter Tubing?
Yes, adding emitters to emitter tubing is not only possible, but also safest for your plants. You can install emitters by creating a hole in the drip tubing using a punch, and pressing the barbed emitter into the hole until the barb locks it in place.
By installing emitters directly into the emitter tubing, you reduce the risk of damaging your plants. Emitters are sometimes installed at the end of a separate piece of tubing, attached to the emitter tubing by a connector. However, if the emitter at the end of the tubing is dislodged, it can cause havoc on your plants.
By installing the emitter directly to the emitter tubing, you minimise the chance of your plants being overwatered by giving the emitter a much stronger and safer connection to the emitter tubing.
What is the Best Drip Irrigation Tubing?
One of the most versatile brands of drip irrigation tubing is the Toro Drip Eze tube. This tubing is specially designed for drip irrigation, is weather resistant and has plenty of flexibility, letting you work around your garden, no matter the size and shape.
Other leading drip tubing brands in Australia include Netafim Techline and Miniscape tubing, as well as Rainbird Copper Shield drip line.
There are situations where you will need to buy specific sized drip irrigation tubing. This can occur if you have existing irrigation that you want to connect to, or to better suit the types of plants you have.
The common sizes of drip irrigation tubing are:
- 12mm (or ⅜”)
- 16mm (or ½”)
- 18mm (or ½”)
- 24mm (or ¾”)
Remember that the fittings are not interchangeable among the different tubing sizes.
Can I Fertilise My Plants Through My Drip Irrigation System?
Yes, it’s possible and very easy to fertilise plants through your drip irrigation system. Using a fertiliser injector, or home fertigation method, you can have nutrients passed through your drip irrigation system, helping speed up plant growth without manually needing to fertilise them by hand.
This article is published for general informational purposes only and does not constitute professional advice. Any action you take upon the information you find on this website is strictly at your own risk. Always ensure you have the right qualifications and certifications to carry out DIY work and never put your safety at risk. Hills Irrigation recommends consulting a professional for all electrical and plumbing work.
Vince is Managing Director of Hills Irrigation and is supported by Lisa in an administrative capacity. Andrew, Isaac and Megan look after the day to day needs of both online and shop customers. As Project Manager, Vince is also responsible for installation projects along with his team. It is his responsibility to work closely with clients to ensure that scope of work is understood and followed.
