By Chris Higgins and Laura Cochran, for LCN

A spray head mounted on a long, black riser is seen here in a test shortly after it was installed at a Southern California shopping mall. Extended risers like this lift spray heads above foliage where they can properly apply water over a planned area. To keep efficiency high, spray heads and rotors should be checked regularly and adjusted to keep pace with shrub growth. Photo by Erik Skindrud

Nothing in the irrigation industry is as common as the plastic pop-up spray head. When the first plastic spray head was introduced nearly 30 years ago, it represented a technological step forward for the irrigation industry. Today, spray heads are used in a high percentage of residential and commercial irrigation systems and are often the first choice for contractors installing an irrigation system.

However, the spray heads and nozzles developed in the 1970s had few features and were not as efficient as those in use today. In this article, we will explore how, over the past three decades, the technology incorporated into spray heads and nozzles has made them far more water efficient and user-friendly than their predecessors.

Matched Precipitation Rate

One of the first significant evolutionary steps in spray head efficiency took place in 1983: Matched Precipitation Rate (MPR) spray nozzles were introduced to the market. MPR nozzles helped save water by allowing users to mix and match different nozzle patterns and radii while maintaining a consistent watering rate. Then in 1984, co-molded, multi-function wiper seals were introduced as a standard feature on spray heads. Additionally, powerful stainless steel retract springs were also added. These wiper seals and springs greatly improved the quality and performance of spray heads by reducing the likelihood of ''stick-ups'' that were frequent with earlier models.

In 1986, built-in check valves in spray heads became available. 1988 saw the introduction of pressure regulation in spray heads. Both of these changes marked sizeable steps forward for spray head efficiency. Check valves eliminated run-off through low lying heads and greatly reduced water waste. Pressure regulated spray heads enabled a constant pressure of 30 psi at the head. The arrival of the pressure regulation function was significant because spray heads and nozzles have always been designed to function optimally at 30 psi. Pressure regulated spray heads therefore optimized the performance of spray nozzles and reduced misting, fogging, and wind drift. When pressure regulated spray heads are used, more water reaches the intended turf or bed area and efficiency is improved.

Planning is especially important when installing spray-head risers. Models like the tall unit at left (and in the photo above) require deeper trenches and water lines. Photo: Hunter Industries

Variable Arc Nozzles

The introduction of variable arc nozzles (VAN) in the1990s was an important leap for many irrigation contractors. While VANs did not necessarily improve the efficiency of spray heads any more than the existing technology of the day, VANs did make landscape irrigation installations much easier and faster. Since an installer could use one nozzle to meet spray pattern needs from 360 degrees to 0 degrees, fewer parts needed to be inventoried and jobs could be completed more quickly. VAN technology has continued to evolve and many of today's VAN nozzles share the same matched precipitation rates as their manufacturer's MPR nozzles.

Plastic spray nozzles that actually reduced watering run times and water use were first made available in 1997. These products, called U-Series nozzles, have a second orifice for more effective close-in watering and more uniform water distribution. The idea of a spray head nozzle with a second opening to facilitate close-to-the-head watering was not a new concept. For many years the brass nozzles that had been used with spray heads featured this type of design. However, the challenges of designing this second orifice into a plastic nozzle proved too difficult to overcome until the eventual introduction of the U-Series nozzle. The U-Series design reduced watering times, saved water and money and reduced waste. U-Series nozzles also featured matched precipitation rates. While some may have found it difficult to get used to the unique spray pattern appearance, the water efficiency and superior results couldn't be denied: U-Series nozzles used 30 percent less water than traditional spray nozzles.

A cutaway view shows the interior mechanism of a spray head riser. When the hardware inside wears out, manufacturers recommend replacing the old riser with a new unit. In a pinch, however, you can replace defective hardware with an interior mechanism from a spare riser.

New Rotating Nozzles

For all the technological improvements made to spray heads and nozzles since the 1970s, the fact remains that they are simply not as water efficient when compared to rotors because they have higher precipitation rates and are more susceptible to wind drift. The most recent technological improvement to spray heads and nozzles deals with the introduction of multi-stream rotating nozzles. These nozzles essentially turn a spray head into a rotor. Affectionately referred to as ''sprotors'' by some, multi-stream rotating nozzles are gaining popularity in the irrigation market for their efficient distribution of water, low precipitation rate, resistance to wind drift and eye-catching aesthetic appeal.

Using multi-stream rotating nozzles on spray heads represent a great step forward in improving the efficiency of spray heads in new installations and through retrofits of older systems. Retrofitting an existing spray head system with multi-stream rotating nozzles is a great way to step up an irrigation system's efficiency. Test results have shown as much as a 20 percent improvement in Distribution Uniformity just by changing traditional spray nozzles on spray heads with multi-stream rotating nozzles.

Most manufacturers have created specialized tools to grasp spray heads and rotors for nozzle replacement. Using standard pliers may work, but can result in damage to the plastic hardware.

Using Rotors with Nozzles

The use of multi-stream rotating nozzles has also served to simplify the use of spray heads in residential and light commercial applications by enabling them to be zoned with traditional single stream rotors. For as long as rotors have been available, contractors and specifiers have been told not to put rotors and sprays on the same zone because of the vastly different precipitation rates. This usually meant installers had to place additional valves in order to properly irrigate large and small areas. However, due to the very low precipitation rate of multi-stream rotating nozzles, contractors can often install them on the same valve with rotors. Some irrigation manufacturers have even taken this concept to the next level. For example, Rain Bird Corporation introduced a line of matched precipitation rate nozzles that fit their 5000 series rotors (25 feet, 30 feet and 35 feet available). When using these nozzles and rotors together, customers can place 5000 series rotors on the same valve with a Rain Bird Rotary Nozzle and have a matched precipitation rate solution. This makes using spray heads easier and more water efficient.

Chris Higgins and Laura Cochran are product managers for Rain Bird Corporation's Landscape Irrigation Division.

Irrigation Insights

2 to 12 : The recommended range of ''pop-up'' spray heads for sprinklers used on residential turf. The height of pop-up should be determined by the height of the surrounding turf, shrubs or other groundcover.