Maximizing Your Irrigation Design By Picking the Right Product

What is the point of installing an irrigation system that isn’t effective. Sure you know how to do the wiring and installation; although sometimes the design is another story. Learn to maximize your irrigation design with Rain Bird.

Irrigation Design Tip: Selecting the Right Sprays, Rotors and Drip Components

The next step in the design process is selecting the right irrigation components for the project. In this tip we will cover sprays, rotors, nozzles and drip components, in later tips we will discuss controllers and valves.

Most of the selection criteria uses the site-specific information gathered or calculated in the earlier steps such as: water source, water pressure, soil type, climate and determining the irrigation requirement. Selecting irrigation components without first gathering this information is premature and can lead to an irrigation system that does not perform to meet the landscape’s requirements and can cause significant performance and maintenance problems.

There are several types of sprays, rotors, nozzles and drip components that you can choose depending on your application. Here’s what we will cover in this tip:

Spray bodies: pop-up and shrub versions

Spray nozzles: MPR, VAN and High-Efficiency Rotary

Sprinklers/Rotors: pop-up and impact

Drip: bubblers, emitters, microsprays and dripline.

In previous Irrigation Design Tips, we identified required information that you need to gather before the selection process begins. Here’s a quick review:

1. Water supply and pressure, and flow limit Each type of component has a performance range for proper operation and these ranges must fit within the available flow and pressure criteria, both of which are a function of the water supply.

2. Climate Areas with special climatic conditions will require special components. Windy areas may demand low- angle nozzles that keep the water near the ground where it resists being blown away. Landscapes in arid climates which experience excessive heat may need either higher flow nozzles or multiple irrigation cycles to maintain the plant material.

3. Soil type and terrain The application rate cannot exceed the soil’s ability to accept water. Low precipitation rate (PR) nozzles may be required to adjust the rate of water application to the intake rate of the soil.

Also, low PR nozzles or dripline can be used on slopes to reduce the potential for runoff and erosion. In addition to any special request by your client or property owner, here are some additional points of consideration when selecting the right components for your project:

1. Size and shape of the areas to be watered. The goal is to select the type of device that will cover the area properly using the least number of units.

2. Types of plant material to be irrigated also dictates which type of component is to be used. Lawns, shrubs, trees and ground covers may all require different types. SPECNEWS March/April 2017 Irrigation News and Product Updates for Irrigation and Landscape Designers

3. Protection of hardscapes or other structures that can’t tolerate overspray.

4. Compatibility of the components used on the same valve. Compatibility is particularly important when laying out laterals or circuiting sprinklers into groups that will be served by the same valve. You want to avoid mixing components with different precipitation rates on the same valve whenever possible.

Why? When components with varying precipitation rates are on the same valve, the owner or maintenance personnel are required to over water one area to sufficiently water another. Even the same type of components may require separate valves to match up water application rate with the rest of the components.

Using matched precipitation nozzles (MPR) allow the same type of sprays or rotors, no matter what arc they cover, to be circuited on the same valve and deliver the same precipitation rate.

MPR nozzles discharge proportional flows of water that match the arc or part of a circle they cover. A full circle nozzle discharges twice the flow of a half circle nozzle and a quarter circle nozzle discharges half of what the half circle unit does. Some nozzles, such as Rain Bird’s Rotary Nozzles have matched precipitation rate with 5000 MPR rotor nozzles – in this case you can use an 1800 Series spray with a Rotary Nozzle on the same valve as a 5000 rotor with MPR nozzle.

Let’s look at some of the applications for various types of irrigation components and examine where they would be best used on a landscaping project.

Spray and Nozzles

Sprays are required for smaller landscaped areas, for areas with enclosed borders requiring tightly controlled spray and for areas with dense tree growth that would significantly hinder a rotating sprinkler’s coverage and for areas that have mixed sections of plantings that require differing amounts of water.

Pressure Regulation and Reclaimed Spray Bodies

Spray bodies with pressure regulation are also available. These sprays ensure operating pressure is regulated to the optimal pressure for the spray nozzle, which will help save water and reduce misting and fogging which is associated with high pressure. Also, sprays for reclaimed water are made with materials that are resistant to chemicals used in reclaimed water for longer lasting performance.

Shrub spray sprinklers and pop-up spray sprinklers often use the same nozzles, but they are mounted on their respective body types. With the availability of 6 and 12 in (15,2 and 30,5 cm) pop ups, some shrub areas near walkways, stairways and sidewalks utilize these units as pop-up shrub sprinklers. The sprinklers pop down after operation, reducing the potential for vandalism and increasing pedestrian safety.

Spray nozzles generally emit single or double sheets or fans of water in a fixed pattern. These patterns are usually a part of a circle or arc. Common patterns include: full circle, three-quarter circle, two-thirds circle, half circle, one-third circle and quarter circle. In addition to the arcs, some specialty spray patterns like center strips, side strips and end strips are available.

Spray Nozzles

Spray nozzles generally emit single or double sheets or fans of water in a fixed pattern. These patterns are usually a part of a circle or arc. Common patterns include: full circle, three-quarter circle, two-thirds circle, half circle, one-third circle and quarter circle. In addition to the arcs, some specialty spray patterns like center strips, side strips and end strips are available. Spray nozzles have an operating pressure range of approximately 15 to 30 psi (1,0 to 2,1 bar) and throw water across a radius of 5 to 22 ft. (1,5 to 6,7 m).

Also available is the variable arc or high-efficiency variable arc spray nozzle, which are adjustable providing coverage from 0 to 360°. These nozzles are intended to handle odd-shaped areas.

Rotating stream nozzles, or rotary nozzles are another type of spray nozzle that distributes water in numerous, individual fingers. These nozzles come in fixed and variable arc models and have an operating pressure range of 30 to 55 psi (2,1 to 3,8 bar) and longer throw range from 8 to 24 ft (2,4 to 7,3 m).

Fan spray nozzles distribute water fairly quickly, with application capability of 1 to 4 in/h (25 to 102 mm/h). The designer must keep this in mind on tight, fine- grained soils, or on slopes, which may not accept water quickly. Rotating nozzles have a more acceptable range for these applications, with precipitation rates from about 1/3 to 1-1/2 in/h (8 to 38 mm/h).

Rotary Sprinklers/Rotors

Available in riser-mount configuration for irrigating larger shrub and ground cover areas, and in pop-up versions for watering turf grasses rotary sprinklers or rotors use various means for converting a portion of the flow and pressure passing through them into “drive” energy to turn the head. In general, rotors have a single nozzle or pair of nozzles.

Part circle units have a reversing or shutoff mechanism to avoid watering outside their arc pattern. Instead of fixed arcs of coverage, most part circle rotors are adjustable from about 40 to 330°, and many can be switched to the 360° (full circle) setting. Full circle only units are also available.

Higher operating pressures are common for rotors compared to spray sprinklers. Available in a wide range of sizes, most rotating sprinklers on the market today operate somewhere in the 25 to 100 psi (1,7 to 6,9 bar) range. Pressure regulating versions hold the pressure at a certain level for best performance and to reduce water use.

The distance of throw is much greater than for spray sprinklers. Rotors can throw from about 20 ft. (6,10 m) minimum for the small units to well over 100 ft. (30,48 m) of radius for larger units. It should be noted that the flow demands for large radius sprinklers are much higher. Discharges of 5 to 100 gpm (1,13 to 22,68 m3/h or 0,32 to 6,31 L/s) or more span the wide variety of flows for rotors.

Despite their large water flow, rotating sprinklers usually apply water much more slowly than spray sprinklers because the water is spread out over greater areas. The precipitation rates for these large sprinklers run more in the 1/4 to 2 in/h (6 to 51 mm/h) range. This makes rotors appropriate for slopes, tight soils, and other areas where slower application rates are desired.

The most easily recognized type of rotating sprinkler is the impact sprinkler. Using a side-driving lever to create rotation, you can mount the impact sprinkler on a riser above the plant material where the stream will be unobstructed over its long radius of throw.

In a large, open lawn area, rotor pop-ups can irrigate vast areas with substantially fewer rotors than spray spray irrigation would require. Like a pop-up spray sprinkler, pop-up rotors retract after operation to be out of the way of mowing equipment and foot traffic. The large radius rotors are usually more economical, and energy and water efficient for large-area irrigation, where their streams are uninterrupted and allowed full coverage. Fewer sprinklers, fewer fittings, and less trenching are definite advantages of rotors compared to sprays – for larger areas.

Bubblers

Bubblers produce short throw or zero radius water distribution. The most common type of bubbler delivers anywhere from 1/2 to 3 gpm (0,11 to 0,68 m3/h or 0,03 to 0,19 L/s) depending on the pressure available and how it is adjusted. The water either runs down the riser supporting the sprinkler or sprays out a few inches (centimeters) in an umbrella pattern. The advantage of a bubbler is that it can irrigate a specific area without overthrow onto other plants. Bubblers can be used in very narrow or small planting areas, and can be adjusted to low flow so large numbers of bubblers can be mounted on one line. There are also stream bubblers, which throw gentle two-to-five foot (0,6 – 1,5 m) radius streams, and the pressure compensating bubbler, which discharges the same flow despite wide variations in water pressure.

The primary concerns for a designer using a bubbler system are to avoid runoff and erosion by confining the water in a planter or tree basin, and to provide proper drainage in situations where an overflow would cause damage.

Drip Emitters and Dripline

Drip emitters and dripline have some of the advantages of bubblers and a few more. There is less chance of runoff or erosion, and very little puddling because of the ultra-low flows of drip devices. The emitter, the most common drip device, is designed to take a water pressure at its inlet of about 20 psi (1,4 bar) and reduce it to almost zero. In this way, the water exits the unit one drop at a time. The most common flow rates for emitters are 1/2 gph (2 L/h), 1 gph (4 L/h), and 2 gph (8 L/h), but there are options for irrigating large shrubs or trees which have flow rates of 24 gph (90.84 l/h). This is a major change from the flow rates for sprinklers. Emitters, in general, are operated much longer per irrigation cycle than sprinklers. The idea behind the application of drip irrigation is to maintain a somewhat constant, near optimum level of soil moisture in the plant’s root zone. This moisture level is constantly available to the plant without saturating the soil.

Multi-outlet emitters, essentially several emitters in one body, use distribution tubing from each outlet on the unit to the desired emission point. Emitters are available with barbed inlets for installation, using a punch on polyethylene tubing, or with threaded inlets for riser mounting.

Dripline has emitters inserted into the drip tubing at predetermined spacing and flow rates. Dripline can be installed on-surface and subsurface. There are also micro- sprays which can be spaced similar to sprinklers but have very low precipitation rates. Precipitation rates of 1/3 in/h (8 mm/h) or lower are common. These fixed arc sprayers can be mounted with adapters on risers or on high pop sprinkler bodies for shrub, ground cover, or individual tree irrigation. For more information on designing drip irrigation systems use the Rain Bird Low-Volume Design Manual.

Performance Data

When looking for an irrigation component in a manufacturer’s catalog, the performance chart for the sprinkler contains several pieces of important information.

The arc or pattern of coverage is usually diagrammed for quick reference so the designer can see if the needed pattern is available in that series of nozzles. The model number of the component or nozzle is called out so it can be specified, by number, in the legend of the irrigation plan.

The operating pressure range of the unit is also noted so that the designer will know the pressure requirements for the performance desired. This range is usually the minimum to maximum pressures under which the nozzle will deliver good distribution of water throughout the entire area of coverage.

Another important number from a performance chart is the radius or diameter of throw. Usually given in feet (meters), this is the actual distance determined by the manufacturer’s testing at the various water pressures listed.

The discharge of the nozzle is given for each pressure noted in the chart. For most nozzles, the discharge is given in gallons per minute (meters cubed per hour or liters per second), and in the case of drip emitters, in gallons per hour (liters per hour). Knowing both the pressure and discharge requirements of the sprinklers is very important.

Some equipment catalogs now include the precipitation rate. This is the water delivery rate in inches per hour (millimeters per hour) at particular spacing. The spacing is usually stated as a percentage of the diameter of the sprinkler’s coverage.

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