Your once-immaculate fairways are now marred by “donuts,” dry patches and/or over-saturated areas. Your best practices have remained the same and the weather has been fairly consistent. What has changed? According to Mark Faris, Underhill International sales and marketing director, these are all signs of poor distribution uniformity, a result of inefficient irrigation.
“The distribution uniformity rate, which is measured by an irrigation audit, indicates whether a sprinkler is delivering uniform coverage and is typically a barometer of turf health,” Faris says. “A low DU rate (65 or lower) indicates that coverage is inconsistent, resulting in donut rings, dry spots or over-watered areas. A high DU rate (85 or better) shows that irrigation application is uniform with green, healthy turf and improved overall appearance. With a higher DU rate, sprinklers can be programmed for shorter run times, saving water and energy.”
Poor distribution uniformity is typically caused by clogged or improperly performing plastic nozzles, rather than a systemic issue with the mechanics of the sprinkler, Faris says. A tried-and-true remedy has been to routinely clean out the clogged nozzles, while also hand-watering the dry patches.
For Michael Kropf, superintendent at The Views Golf Club in Oro Valley, Ariz., his course’s entire irrigation system was replaced about 10 years ago because of poor distribution, as well as continual leaks and blow outs. Also, the course was converting to reclaimed water at the time, so it took the opportunity to have a new system to help prevent turf damage. The old system was lacking head coverage, had an assortment of heads ranging from old-fashioned impacts to new drive units and the central control was outdated and lacking accurate details.
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Arc adjustment There is a fine line between sprinklers providing too much coverage and not enough. That said, there is potential harm in adjusting the arc incorrectly. For Michael Kropf and his desert golf course at The Views Golf Club, this is not a task to be taken lightly. “We do a lot of arc adjustments,” he says. “I only overseed fairways, tees, greens and aprons around greens, so we adjust arcs to where the ryegrass needs water and away from the dormant rough areas. “Also, during the summer, we do a lot of adjustments with the cart path edges,” he adds. “Water going across the path into the desert is a waste of water and creates a lush desert needing more maintenance. I’m a big believer in hard edges. I really think crisp edges make the golf course look that much better, so I put a big emphasis on maintaining them. An easy way to keep nice edges is to continually check and maintain sprinkler arcs. Heads that are too tight leave brown areas down the whole fairway, but heads that are too open waste water and create different maintenance issues.” Depending on the desired outcome, there are two ways to adjust Kropf’s sprinkler arcs. “Rain Bird adjusts with a hard side and an adjustable side of the sprinkler,” he says. “Using a small screwdriver turns the adjuster on top of the head either opening or closing the arc. To change the hard side, the sprinkler needs to be removed from the main body and manually turned either direction to open or close. “Along edges we open the head one notch off the edge to allow for wind,” Kropf adds. “If the arc is set exactly on the edge of the grass, we tend to have damage to the turf from lack of water which looks very ugly down every edge. However, if the arc is too open, then we are wasting water into the desert, which is a large waste and leads to wet muddy areas around the cart path edges that are also very ugly.” While irrigation systems are vital to the overall health and appearance of turfgrass, superintendents can rest easy knowing that the process of setting sprinklers to grade, adjust arc and replacing nozzles are all fairly straightforward — if not labor intensive. |
When setting their sprinklers to grade, Kropf’s team takes the extra effort to make sure the job is done correctly.
“We have decomposed granite mixed with sand-type texture soils, so the only efficient way is to dig up around the swing arm and raise the head to grade,” Kropf says. “We use a 2x4 to level the head with the surrounding area and then pack the soil back around the swing arm.
“We have Rain Bird 700, 750, 751 and 550, heads which all share the same sprinkler body, so the wiring is placed near the communication tube,” he adds. “The wires are placed low enough that they are not clipped by sprinkler head edging, but high enough they can be accessed fairly quickly for troubleshooting. The sod is laid back around the head slightly above grade to allow for settling.”
The process is labor intensive and time consuming, but it beats the more “advanced” mechanical option.
“We tried using the hydraulic machines that use a probe that injects water around the swing arm and uses hydraulic pressure to pull the head up, but the soil doesn’t compact back around the swing arm,” Kropf says. “Over time, the head settles right back down. We found the time it takes to dig up a head and pack the soil wasn’t much different than using the hydraulic pullers and never have to worry about it settling.”
As with any potential hazard to turf, waiting for damage to appear is not the prudent way to discover problems with an irrigation system.
Kropf takes a proactive approach. “I have my irrigators try and check heads on two holes a day during down times,” he says. “This check involves turning every head on with the satellite to make sure all the electrical components are working correctly from the satellite to the head. Then they manually turn on every head to check for arc adjustment, spray pattern and pressure.
“Our water is reclaimed, so we have problems with ciliated protozoa clogging heads and nozzles, as well as small rocks getting stuck,” Kropf adds. “Usually the visual inspection will show whether the head is working properly in regard to nozzle performance. If a nozzle is clogged or worn, the spray pattern is very different.”
Kropf’s team will first look to repair nozzles that are not functioning properly (having nozzles that thread and are easily removed and repaired), but it is sometimes better to just replace a faulty nozzle.
“We replace nozzles when they are worn out or damaged,” he says. “We can remove debris from them easily, so most of the time that is all that is required. Costs aren’t prohibitive if only a few nozzles need replaced. However, if the nozzles are showing considerable wear across the entire golf course (that) would require adding to the irrigation budget. We have approximately 2,500 heads ... at about $3 per nozzle assembly is several months of my operating budget. That is why we do a lot of preventative maintenance on the irrigation so we replace as required instead of waiting until there is a widespread problem.”
Replacing a faulty nozzle is a simple procedure. “The nozzle is easily removed by threading it out of the nozzle housing,” Kropf says. “The sprinkler is removed from the sprinkler body and the nozzle is simply unscrewed with a tool that fits around the nozzle.”
Replacing original equipment manufacturer nozzles is fairly easy, according to Faris, taking about three to four minutes to conduct both a main and intermediate nozzle change-out. “First, remove the sprinkler cap to gain access to the nozzle base. Depending on the OEM design, this may require a secondary operation to remove the nozzle base from the nozzle cap. Remove the OEM nozzle with a small pair of water-pump pliers. Wipe the inside cavity of the nozzle of any grit or sediment and press fit the new nozzle into place,” he adds. “Align the nozzle depending on the application and sprinkler model. Re-install the nozzle cap assembly.”
Faris cites a two-year study by the Center for Irrigation Technology (California State University, Fresno) to stress the importance of properly working nozzles. Conducted at a series of courses, the study found metal nozzles improved distribution uniformity and reduced water consumption in one season by an average of 6 percent, and up to 20 percent on some sites. Water savings of 6 percent on a golf course can add up to 800,000 to 9 million gallons per course per year, depending on location and rainfall, and also were successful in preventing wind drift, Faris says.
Rob Thomas is a Cleveland-based writer and frequent GCI contributor.
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