Sprinkler heads come in a variety of sizes, shapes, models, and brands, but most of these variations fit into four main categories:
- Pop-up sprinkler heads
- Impact rotors
- Gear-driven rotors
- Large turf rotors
Pop-up Sprinkler Heads
Probably the most widely used irrigation head; pop-ups are typically used for residential and small commercial sprinkler systems. There are two types of pop-up heads; stationary sprays and rotating heads, called rotors. Pop-up spray heads are designed to supply a continuous stream of water, and are fitted with a nozzle. There are nozzles in a variety of designs; each design is for a specific spray pattern, such as a full arc, a half-circle, or a quarter circle. Nozzles are used to distribute water in a variety of patterns to fit the contours of the landscape. Other than a pop-up stem, pop-up spray heads are stationary, and are inexpensive and simple to operate.
Pop-up sprinkler bodies range in height from 2 to 20 inches. Two-inch pop-ups are common in areas with tough soil where digging is difficult. Four-inch pop-ups are commonly used in turf areas; the current standard for mowing height in lawn areas is about three inches – a four-inch pop-up provides sufficient clearance for a growing lawn and for sinking – it is common for sprinkler heads to “settle” over time as soil and thatch build up around the sprinkler head. Six to twelve-inch pop-ups can be used to irrigate groundcover, gardens, and shrub borders; risers can be installed under spray heads as the landscape grows and greater clearance is needed.
Pop-up spray heads are designed to cover relatively small areas with spray radii between 3 and 15 feet, and an operating pressure between 15 and 30 psi. The precipitation rate of fixed spray heads is dependent on system pressure, spray head spacing, manufacturer specs, and nozzle size, and varies from 1to 2.5 inches per hour.
Manufacturers are continually improving pop-ups: features such as matched precipitation rates, adjustable and low trajectory nozzles, and nozzles with square spacing and strips are some of the more recent contributions to sprinkler efficiency. Several manufacturers have even developed nozzles that convert a pop-up spray head to a rotor capable of covering distances ranging from 8 to 30 feet. The advantage of these nozzles is that they reduce the precipitation rate, which improves water absorption and reduces run-off.
Impact rotors provide single or multiple streams of water to the landscape and distribute water in an arc pattern typically ranging from 40 to 360 degrees. They are designed to cover larger areas than pop-up spray heads; the spray radius for most rotors is 20 to 150 feet with a precipitation rate between 0.1 to 1.5 inches per hour.
There has been very little change in the design of impact rotors over the years; its uncomplicated design makes it suitable for areas with well water or where other types of heads might get gummed up by hard water. The radius and arc are easily adjusted; however they require regular maintenance and the spring mechanism is often too noisy for residential sites. Because impact rotors are often made of bronze or brass, they may cost twice as much as a plastic, gear driven rotor; however, they can last for years, and have a much long “field life” than plastic rotors.
Gear-driven rotors are one of the most commonly used sprinkler heads for medium- to large-scale sprinkler systems. Their low cost, quiet operation, and versatility are a few of the advantages that gear-driven rotors have over impact rotors. They typically require less maintenance because the enclosed body design prevents clogging of the drive mechanism from dirt and other debris.
Gear-driven rotors are best suited to small commercial sites or large residential areas. They work better than pop-up spray heads in areas with slopes or clay because their lower precipitation rate increases water absorption.
Gear-driven rotors use nozzles, and it is becoming more and more common for manufacturers to provide a nozzle tree with each of their rotors. This makes it easy to select the appropriate size nozzle for the desired radius and precipitation rate. Typically, gear-driven rotors have a radius that ranges from 18 to 55 feet and an arc rotation from 40 to 360 degrees. Operating pressures range from 25 to 75 psi and precipitation rates range from 0.2 to 0.8 inches per hour depending on the pressure, nozzle size, and the layout of the zone.
Large Turf Rotors
Golf courses, parks, and some commercial properties require large turf rotors. These rotors require an operating pressure of 50 to 100 psi, and can cover radii up to 100 ft. with flows as high as 80 gallons per minute. Older model golf course heads were made of brass; some of these heads are still operating in the field 40 years after they were originally installed. The high cost of brass heads has made plastic heads a common choice.
One of the major differences between the sprinkler heads used for residential and small commercial irrigation versus large turf rotors is their actuation. On smaller sites, sprinkler heads are laid out in a block formation and several heads are activated at one time when either a manual or electric valve is opened. The high flows and flexibility required on large sites make this type of layout cost prohibitive. Instead, most large turf rotors use either electric valve-in-head (EVIH) or hydraulic actuation. EVIH actuation generally has fewer problems than hydraulic activation and is the most common actuation system for large-scale application.
The highly competitive irrigation manufacturing market benefits homeowners, landscapers, and other irrigation professionals. This competitive market continues to produce design improvements and innovations, increasing the durability of sprinkler heads and reducing costs. Advances in nozzle design decrease overspray, runoff, and wind dispersal.
Knowing the conditions and requirements of the site to be irrigated is an important step in finding the right sprinkler head for the job. Soil type, water pressure, water source and weather conditions are just a few of the many factors that affect sprinkler head selection. After acquainting yourself with these factors, familiarizing yourself with the four basic designs of sprinkler heads will have you well on your way to making an informed, cost-effective selection for your sprinkler system.
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