May 24, 2002
Clip 'n Keep:
Which sprinkler is right?

By Lorne Haveruk, C.I.D., C.I.C., C.L.I.A., Water Management Services Inc

Do I use a micro or a dripper? Should I use a soaker or a drip tube? How about a bubbler or a flooder. I think this area needs a mister, a spritzer or a spray. The other location should use an impactor, a gear or a large rotor to water everything all at one time. Should it?

     Each piece of irrigation equipment is designed to perform a certain task. If you know what task the device was designed for, you can properly choose the right equipment. To have the system perform you must design it for the right application. This influences the operational efficiency of an irrigation system immensely.

     Why irrigate? Most applications require us to irrigate due to lack of precipitation in the form of rain. Have you ever stood in a rainstorm where you were wet on the top of your head, shoulders, back, and down your legs, but the rest of your body was dry?

     If you were a plant in an area left dry, you would not grow as well as in the areas that received the rain. The performance application efficiency of this rainstorm with missing 40 per cent of your body would be rated as an average to good irrigation system. This is very common with many of today's older and just installed irrigation systems. Why?

     Not knowing the equipment available to create our systems, we can not hope to create the ultimate watering machine. By the end of this article you will better understand the application devices that can have a profound effect on the efficiency and operational cost of your irrigation system(s).

     Soaker hose and drip tape serve the same purpose in different ways. A soaker hose pipe connected to a distribution pipe (which does not emit water) needs to be connected to a pressure compensating device and a filter. Without these two items the pipe can rupture and become plugged over time. A soaker hose leaks water along its full length if installed correctly. This product works well for hedges and mass planting areas in narrow beds or road medians. A drip tape delivers water through a network of tubes using built-in emitters spaced at 12", 18", or 24". The drip tape is very useful when you know your soil type as you know how water will percolate within the root zone soil structure and spacing of the plant material. It has been proven to increase crop consistency and yields while reducing water consumption for growers around the world. Knowing your soil structure and plant spacings will enable you to determine which spacing works best for your application.

     Drip systems efficiently deliver precise amounts of water to plant root zones. These devices and systems are best suited for potted plants and beds where the plants are spaced out rather than massed together.

     Single and multi-outlet emitters are available in a variety of flow rates, spacings and patterns to meet varying water requirements.

     It is very important to use pressure compensation devices combined with an inline filter upstream from the first drip components to ensure the longevity of the drip emitter, zone or entire system.

     With the increase in use of drip components on many residential and commercial projects, you must perform routine maintenance on the irrigation system, regardless of the distribution devices used to ensure the system continues to operate as designed. Periodically, the systems will need to be retrofitted (redesigned) to ensure the system operates at optimum performance levels, which help to keep operational costs in line.

     As the cost of water and demand for clean water increases, new products continue to be developed which allow professional irrigators to come up with innovative ways to deliver results while using less water.

     A low volume microspray can be used to retrofit existing spray sprinklers and shrub adapters. These maxijet micro sprays come with pressure compensation and screens to adjust pressure and prevent clogging. The low flow rates reduce runoff in compacted soils and deep percolation of water passing below the plants' root zone in sandy soils. Optimum operational conditions are 20-50 Psi, 10-24GPH, with radius of coverage at 4'-6'.

     A bubbler's primary use is for irrigating trees, shrubs and flowers in small confined planters. With a fully adjustable flow from 0-2.3 GPM, these devices are used in a zone with spacings from 1-3' or close to each individual plant. They apply water very quickly when fully open, and are not to be combined with any other type of sprinkler due to the varied application rates of bubblers and spray sprinklers

     Spray sprinklers, sometimes called misters, are the backbone of the irrigation system. Only within the last 20 years have the more modern impact and gear type rotor sprinklers become available to the commercial and residential marketplace. Prior to this time, most irrigation systems were installed by plumbers, using copper pipes and brass 1" pop-up spray sprinklers to distribute the water. If these systems were properly maintained, they are still operating today as they were designed many years ago.

     Modern spray sprinklers come in varying pop-up heights from 2" to 12" to water close to the ground in windy conditions or to rise above the plant material to distribute water evenly over the intended area of coverage. Designed to be used in almost any application, they have an area of coverage from 3' to 17' with an operational pressure range from 25 to 70 psi.

     At the upper end of the pressure scale, misting will occur. Mist is very easily blown off-course by a slight wind or even the operating pressure of the system.

     If there is a component of an irrigation system that you need to know, it's nozzles. MPR, PC, VAN, U, and other acronyms are common place in today's highly technical irrigation water conservation business. Matched Precipitation Rate nozzles simplify the design process by allowing sprinklers with various arcs and radii to be mixed on the same zone station or circuit. A ¼, ½, and full circle spray sprinkler will all deliver the same rate or amount of precipitation over a given area if designed, installed and used correctly. This allows for an even distribution of water.

     Pressure Compensating nozzles, screens or sprinklers balance the varying pressures at the sprinklers throughout the zone so each sprinkler is watering using the same pressure. This allows each sprinkler to perform the same if all other considerations in the designing process were handled properly.

     Variable Arc Nozzles are adjustable nozzles for all standard and irregular-shaped turf, plant and shrub areas where a spray sprinkler would be used. They are adjustable from 0 to 360° and cover areas from 4' to 15'. Operational pressures range from 15 to 30 psi, with 30 psi being the optimum pressure for the sprinkler to perform at its highest efficiency level.

     U - Double Orifice nozzles are relatively new to the marketplace and were created to provide close-in watering beside the sprinkler while delivering a more uniform water distribution throughout the area of coverage. Spaced from 9'-15' with a pressure range of 15-30 psi, these nozzles are easily interchangeable with standard nozzles.

     Gear driven full or part-circle rotor pop-up sprinklers are another backbone of the irrigation industry for turf applications.

     Used primarily for the distribution of water over areas ranging from 20'-35' on residential and commercial properties, they can also be used to water large shrub and plant beds where falling water will not hurt the plants.

     Most gear sprinklers are available in pop-up heights from 3"-12" and are adjustable from 30 to 350°. Full circles are used for 360° watering purposes. Nozzles are available for these types of sprinklers regardless of the manufacturer. Operating ranges are from 25 to 65 psi with application rates from 0.50 to 9 gpm. Precipitation rates vary from 0.20 to 1.81 inches per hour, depending upon spacing, nozzle selection and operating pressure.

     Impact rotors are the easiest medium-sized sprinklers to use and adjust. They are primarily used on residential or light commercial properties.

     Impact sprinklers are especially noted for superior performance with effluent or dirty water from lakes, rivers, ponds, etc. There are no internal workings so the impact sprinkler will not jam up with debris. Even silt will cause sprinklers to stop operating over time. These sprinklers have one of the best water distribution patterns on the market and are noted for close-up watering during the return cycle. Operating ranges are from 25 to 60 psi, watering 22'-45', with a flow rate of 1.5-8.4 gpm. Precipitation rates vary from 0.28 to 1.17 inches per hour.