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What drip emitter to select for my garden

As you get ready to buy and install your first drip system, or to extend a system, you may decide to see what is available on the internet or you may go to a home center near you to find the prefect drip emitter devices for your garden. You may be surprised that there are so many different types of emitters, flow rates, and shapes; ouch! What should I use, at what flow rate, how many will I need?

This article will try to clarify the issue of how to select the right drip emitter for your garden.

Drip emitters come in three styles: adjustable, pressure compensating (PC) and non-compensating with labyrinth or spiral water passage.

1. About Drip Emitters:
Pressure Compensating (PC) Drippers give the same amount of flow within a range of pressures (for example a dripper will be rated at 1 GPH between 10 and 55 PSI). PC drippers are available with flow rates of .5, 1, 2, and 4 GPH. Pressure compensating drippers may have a self-flushing mode in which, during the system start up and shutdown, the flow increases and allows the dripper to clean itself. This equates to a longer life span and better constant flow during the lifetime of the dripper. The main use of the PC dripper is on systems with a long run of driptubing, to maximize the amount of drippers on a single dripline while maintaining an even flow rate from each dripper. They are also better suited for landscape areas with elevation differences. Lastly, from a conservation point of view, they allow for good control of the total amount of the water used (for example, one hour of use with 100 1-GPH drippers will give you the exact total flow rate of 100 GPH, no more, no less).


Pressure Compensating Drippers
Four Outlet PC Button Dripper with Stakes

Non-Compensating Drippers are available in .5, 1, 2, 3, 4 GPH. The non-compensating drippers will discharge the same amount of flow at a constant pressure of around 15 PSI. In other words, the higher the pressure the more flow the dripper will release from the dripper, and at lower pressure, less flow will be release. The non-compensating drippers cannot be self-flushed, and therefor will need a filter with a pressure regulator at the beginning of the line. The non-compensating drippers work well in smaller systems with short runs, and where no differences in elevation occur.


In Line Button Dripper
Button Dripper with Stake
Button Drippers
Flag Drippers

Adjustable Drip Emitters are available in adjustable discharge ranges from 0-10 gallons per hour (GPH) at a constant pressure. As pressure changes, the flow rate also will change. These devices have the flexibility to allow adjustment of the flow rate for each individual plant, as the plant grows. Twisting the dial on the top of the adjustable dripper towards the "+" or the "-" signs will allow an increase or decrease in the flow. The adjustable drippers have a 360-degree flow pattern cap that produces a gentle stream pattern, which can be adjusted from a small to large coverage area by rotating the dripper cap.

The advantage is the adjustable feature; the disadvantage is also the adjustable feature. As you adjust the flow you lose control of total flow rate. In other word The number of adjustable dripper that used can limits the efficiency of the system. For example, if used on a 1/4" microtubing, only as few as three to four adjustable drippers can be used when open to the maximum flow. when used on 1/2" polytubing 22 to 25 can be used


Adjustable Drippers

Drip irrigation has a wide range of applications. It is adaptable to different terrain, different planting configurations, such as vegetable gardens, container boxes, patios, vines, shrubs, small to medium size trees, greenhouses, and nurseries.

2. Where to Use Drip Emitters
Existing Garden: An above ground drip system, perhaps covered with mulch, alleviates the need to dig a trench and potentially damage existing plant roots.

New Landscape: Easy to install, drip irrigation is ideal for new landscape areas where plants with similar water requirements may be grouped together for better water use and conservation.

Vegetable Gardens: A drip irrigation system is ideal for row planting. It creates the perfect growing conditions, as well as reduces weeds and pests, which is especially important in a vegetable garden.

Windy Locations: Windy days can cause the sprinklers to throw the water far from there locations; by using a drip system you apply the water only where and when it is needed,

Odd Shaped Area: In oddly shaped areas where sprinklers are especially inefficient, drip irrigation can provide an ideal solution, eliminating runoff and wasteful spray.

Containers and Baskets: Drip systems are ideal to use in hanging baskets or planters by using, and by extending, the 1/4" microtubing to planters. Add a PC, non-PC, or adjustable dripper and secure with a stake.

Greenhouses: Instead of watering by hand, use multi-outlet drippers with microtubing to cover a large amount of pots or baskets at once, Drip irrigation will help deliver a precise amount of water to each plant or container

Now that we know about the different drip emitters and where to use them, the last question is what dripper to use?

3. How to Select the Right Drip Emitter:
This decision should be base on the needs of the plants. If we understand that plants need lots of water, that we like to see the water flow, and we should like to apply the water fast, then the solution is the adjustable dripper. It allows you to adjust, and apply a large amount of water very quickly. Remember it can also limit you to being able to use a limited number of these devises (maximum of 22 to 25 adjustable drippers with full flow on 1/2" driptubing).

Pro: They are easy, adjustable drippers can be adjusted for any size plant, and only one per plant is needed.

Con: No control on total flow rate, limited capability of the system. If open wide, as in most cases, it will saturate the root zone quickly. This will have some damaging effects on the plants, if left open for too long. Also, with the use of one dripper fully open per a large plant, it will not cover the root zone area required, and a second dripper may be needed to water the root zone.

The other two options are using a PC dripper or non-PC dripper. these are the ones that we like to recommend. Either of the two options provides the flexibility and the features that make low flow and controlled drip irrigation better then many other methods of watering.

Controlled amounts of water flow, the method applied, and the soil's physical and chemical properties determine the plant's ability to remove water and nutrients from the soil. This method is used very extensively in agriculture today because using low flow drippers with the same flow rate will allows long run with equal flow rate along the line. Example:using PC drippers with 1 GPH spaced every 4' allow a distance of up to 800'.

Note that as a plant in the landscape grows, its root zone will grow. Additional same-flow drippers can be added to cover the new growth of the root zone area. In this method we use one dripper per small plant up to 10", two drippers for a plant up to 20", three drippers for a plant up to 30", and we continue to add drippers as the plant grows.

The closest spacing between dripper should not be less then 10"

Pro: With a measured flow rate over a period of time we can control the soil moisture content for growth. With a single flow rate we can water small and large plants, cover a large area from a single water source, have total control of flow rate used, and, as the plants grow or the weather changes, we can adjust the total flow rate for the whole system by turning the water on for a longer or shorter time.

Each type of soil will require a different layout. In sandy soil, the water will tend to go straight down, so use closely spaced (10" to12" apart), 1 GPH or 2 GPH drippers and run two-time a day. In loamy soil, the water will move slowly and will spread evenly, so here you can use .5 GPH or 1 GPH drippers with a 16" to 18" spacing. In clay soil, the water will be absorbed very slowly, so use low flow such as a .5 GPH dripper at a wider spacing, 18" to 24" apart.

Con: The system will require 150-mesh filter and a pressure regulator required when PC and non-PC dripper are used. The system will also need to be flushed periodically to prevent accumulation of debris.