Detectives of irrigation
|By Mary Elizabeth Williams-Villano|
The methods and skills required to detect irrigation system problems are like solving a Sherlock Holmes mystery.
When I was in high school, I read all the Sherlock Holmes stories I could get my hands on. It was fascinating how the great detective eliminated first one possibility, then the next, and the next, until he figured out exactly what happened and “whodunit.” How, from a cigar ash, Holmes could deduce what type of cigar produced it, where it was bought, and even some of the smoker’s personality traits.
It may never become the source material for a major motion picture, but an irrigation troubleshooter is also a detective. He looks at the clues he’s seeing at the “crime scene,” and, calling on his experience and knowledge, pieces together the puzzle. He checks out one probable cause, rules it out, then moves on to the next possibility.
Simple and logical. If only that were true. But there are “wild cards” out there in the field that can throw you for a loop. As Holmes once said, “Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.”
In general, with irrigation systems, the truth will fall into one of three main categories: mechanical, electrical or hydraulic.
For Tim Black, CIC, CID, CLIA, CIT, owner of Irrigation Tech, Rochester, New York, the investigation begins with skepticism about the first eyewitness account. “Every time I show up to a troubleshooting call, I know that what the person tells me the problem is, isn’t really the problem,” he says. “For instance, a person will say, ‘I have a leaking head’ but there’s really no such thing; what they really have is a leaking valve.”
In fact, this sort of thing happens so often that it’s become an inside joke. “That’s one of those things we laugh about — what we refer to as a ‘Mr. or Ms. Homeowner’ call. What they mean is that it’s slow-leaking, and the only way for that to happen is if water is dribbling by the control valve,” says Black. “That is always a mechanical problem.”
But these investigations can be so complex that even experts will disagree. Craig Otto, CIC, CID, CIT, CLIA, CLWM, owner of Irrigation Otto, Big Lake, Minnesota, and a technical trainer for the Rain Bird Academy, says “I’m not sure that I would agree 100 percent that a leaky head is really a valve problem. Sometimes sprinklers will lose a nozzle. Another thing that’s fairly common with rotors is you can get a weepy seal, especially if they’re older rotors.”
“Anytime we do a troubleshooting class, we emphasize that there’s a strategy to this,” says Chris Pine, CID, CIC, CLWM, CLIA, CIT, MCLP, CLVLT and president of BluGreen Solutions and a partner in IrriTech Training, Pocasset, Massachusetts.
“You isolate exactly where the problem is through a process of elimination. It’s the same process, whether it’s a traditional irrigation system or a two-wire.”
Pine says he’s one of the people who gets called when a contractor is completely stumped. “A guy called me a couple weeks ago saying, ‘I’ve been in this business for 25 years, but I just can’t figure this out.’ I took him through the process and it turned out that the problem was in the controller. Almost every time, if you narrow it down using this process, you’ll find the source of the malfunction.”
You start with the easiest thing to eliminate first, says Black. “Let’s say you have a zone or multiple zones that will not activate. That could be the controller, the wire path, a valve or more than one valve.”
Once you determine that it’s zone A that has the problem, you next need to find the valve and activate it to verify that it does, indeed, belong to zone A. Once you think you’ve isolated exactly what’s causing the problem, you confirm it with a test so you don’t end up fixing something that isn’t broken.
The ohmmeter tells (almost) all When David Clarke, CIT, CIC, CLIA, CLWM, a commercial irrigation service tech at JB Lawn Sprinklers Inc., Wilmington, North Carolina, goes on a call, he makes sure his ohmmeter goes with him.
“The first time I visit a site with a traditional, non-two-wire system, before turning anything on, I go right to the controller, take ohm readings and write them down. Very quickly, it’ll give me little clues before I start trying to run the system and end up driving laps around the neighborhood chasing after ghosts.”
The ohmmeter readings can tell him, among other things, that there might be two valves that have been wired together. That could explain a pressure problem before he even starts counting the number of heads or figuring out the gallonage. Maybe a wire became disconnected or damaged in a place where nobody could find it so someone just jumped that valve’s connection over to the next one.
“Often, valves end up wired together for just that reason,” says Clarke. “We’ve seen a lot of two-valve combinations that were done in an attempt to keep a pump from short cycling. That almost never works.”
Pine says the simplest way to determine if a problem is electrical is to remove the electricity. If the problem stops or doesn’t exist at the point, you can assume that it’s an electrical problem and begin isolating it.
Let’s look at a common problem, a zone that’s not coming on. Following the method of starting with the easiest thing, Black first finds the number of that zone on the controller, activates it and checks the voltage. “60 seconds later, I’ll know if the controller is the source of the problem or not.”
“Now, let’s say the controller is working properly,” says Black. “The next thing I’m going to test is the wire path. I’m going to turn the controller back off, and then I’m going to get my ohmmeter and take a resistance reading from that point, at the controller, out to the field. A proper resistance reading will be between 30 and 60 ohms. It can be slightly below that or slightly above, but it needs to be darned close to that.”
“If it’s good, then I know I’m going to have to find the valve, and that may mean I’ve got to break out my tracking equipment because usually I don’t know where it is. I may have to spend a good chunk of time tracking down that valve.”
If, on the other hand, he’d gotten a resistance reading that was too high or too low that would give him a clue as to where he should start looking next. An ohmmeter reading of infinity could mean that the solenoid on the valve is totally shot, maybe from a lightning strike, or that the wires out to that zone or zones were cut by a shovel. He’d get the same result from both, but in either case, he’s at least narrowed down what the problem is likely to be.
Black says if you know where the valve is, you can eliminate one possibility fast. “You go to the valve, turn on the voltage again and pull the wires off the solenoid. See if it’s getting voltage and read what the resistance is through that solenoid. If it still doesn’t work, now you’ve narrowed it down to the wire path, somewhere between the valve and the controller.” Then, you may have to pull out some of what Black calls “the cool toys we have in our industry,” a wire tracker and a fault finder. If a wire path is leaking voltage to ground, these tools will tell you exactly where it is.
If a zone keeps running and running and won’t shut off, it could be that a valve is stuck in the on position, according to Black. That can be either electrical or mechanical, so once again you start with the easiest thing and test that the controller is sending voltage to that valve.
“A voltage spike or lighting hit can scramble a controller,” Black says. “I’ve come across some that have been zapped, and they were sending voltage out to all the zones. That’s a problem. In that case, turn all the power off to the controller, including the backup battery, then power it back up again and it’ll probably be fine.”
If you’re pretty sure it’s a valve problem, start by analyzing the symptoms, Black says — not opening, not closing or leaking — to figure out what’s going on inside the valve. It’ll often be some type of a problem with the diaphragm not opening or closing.
A valve could be stuck on because a bit of debris got wedged under the diaphragm. “You can make the diaphragm lift higher than it normally does by turning the solenoid open or by using the bleeder screw,” says Black. “By doing that and then closing it again, it’ll wash out whatever the object was. If you get away with that, you’ve just saved yourself gobs of labor.”
“Usually that problem has something to do with the water on top of the diaphragm, what we call the pressure chamber,” says Black. “But let’s say that’s not the problem — then you probably have a mechanical problem at the valve, which means now you’ve got to find the valve, turn off the water, open the valve and see if something’s stuck in it that you can just remove. But if it’s damaged the valve, you’ll have to replace all or part of it.”
The goal here is to be able to repair the valve without having to replace it. If you can analyze the symptoms, you can often avoid that outcome.
Hydraulics or do the math
If the problem isn’t electrical or mechanical, it’s hydraulic. “A hydraulic problem, such as a real leak, has to be ruled out first,” says Clarke. “If you verify that you don’t have a leak, then you have to figure out how many heads and how many gallons per minute the zone is trying to use and compare that to what size pipe it’s built out of and how far away from the source it is.”
What you’re looking for, according to Clarke, is a design flaw, or some change that might’ve occurred after installation that made the zone not function properly anymore — things like adding too many heads to a zone or using oversized nozzles during a repair. This is very common especially on properties that have had many different irrigation caretakers over the years.
He says, “You have to learn the limits of the way that it’s piped and see if you can get it back to full pressure functionality before trying to analyze coverage or before you think about adding heads, adding a valve, or whether you need to add a ‘hold zone’ or split a zone in half. That’s a challenge without a map because once you get past the valves, you can’t use a wire tracker. You have no idea where that pipe is, other than the fact that it’s connected to those heads.”
Hydraulic problems can also be caused by too much flow through a pipe resulting in too much volume. Or too little flow because of some restriction of the pipe.
Black will sometimes put his ear to the ground, like someone in a western film, to hear restricted flow. “I’ll listen somewhere between the heads that work and the heads that don’t. You can hear where the flow is being restricted; it can be quite loud.”
“What I’ll often find is a big, nasty wad of roots. They’ll get so fat that there’s no void space between them and they’re like a solid mass of wood, crushing the pipe. All our service trucks have a battery-powered reciprocating saw and lots of long blades. You just stab them into the ground and start cutting.”
Once you’ve learned the system, you can stop asking the client questions and start telling him what his options are, Clarke says. “The beauty of hydraulics is that two plus two always equals four. If you can’t add any more heads to the zone, and you’re confident in your math, then you can simply tell people that.”
“One of the best ways to determine that is by measuring pressure differences in the system, but not a lot of contractors do it,” says Pine. “You need to have either a tool that measures pressure at the sprinkler or at another connection to the pipe to determine how much pressure loss occurs over a certain section of pipe. That’s an easy way to isolate, specifically, where the problem exists.”
Clarke catalogs the hydraulics of a system he’s working with. “I start by figuring out what the yield of the water source is, what size the main line is and how far away from the assignment it is because distance affects the pressure that I have to work with.
Then as I’m running the zone or zones I’m looking at, I’ll do a basic head count and estimate how big the zone is in gallons per minute. I compare that to the water source and the mainline size and start getting an idea of how much water I have to work with, and what I can get away with.”
Clarke adds that “a lot of installers don’t know much about design hydraulics. They won’t take into account the pressure loss over distance that friction causes and that throws off their piping calculations.”
When Chris Pine teaches troubleshooting classes for the Irrigation Association, he explains that there are only three areas that can go electrically wrong in a conventional, non-two wire system: the controller, the solenoid or the field wiring. “To isolate which one of those it is, we test the power as it moves from the source all the way out to the solenoid. We check to see whether the controller is producing power output for each one of the valves.”
“If it is, next we look at the field wiring and the solenoid,” continues Pine. “With a multimeter, we test the resistance of both. If there’s a fault, and both the field wiring and the solenoid test bad, at that point we’ll go to the solenoid and see if that’s really the source of the problem. If the solenoid really is bad, then we know it isn’t the field wiring. But if the solenoid is okay, then we know it is the field wiring.”
Clarke says, if you don’t have a funny ohmmeter reading and you know for certain that a wire goes to the area you’re working on, then you need to figure out what happened to that wire. It could be a bad splice or damage to multiple wires.
The next thing, Pine says, is to look at context clues. Are other wires also giving zero readings? Or are there wires running valves that are in that same area? Sometimes it’s easier to find the next closest valve and try and pick up some clues from the wiring in that valve box or manifold; that’s often simpler than hooking up a tracker from the controller and seeing what happens from there.
Clarke says, “Sometimes, you have to kind of break things into pieces. If you’re far enough away from the controller to where you’re losing signal, there might be a splice or junction box between the controller and the zone you’re working on where you can identify the wire you’re looking for and hook your equipment up to it to improve your tracking signal, or just take your readings from there.”
Troubleshooting irrigation systems isn’t easy, but if you’re a person with an investigative mindset and a bent for problem-solving, it can be a very satisfying and challenging task. And the kinds of skills involved in it are very much needed. Armed with education, certification and experience, you can be excited every day to shout, “the game’s afoot!”
Tech tip: Check the controller with an ohmmeter before you do anything else and write down the readings. They will give you clues that can save you lots of time.
Don't forget: There are only three areas that can go electrically wrong in a conventional, non-two wire system: the controller, the solenoid or the field wiring.
The author is senior editor of Irrigation & Green Industry magazine and can be reached at firstname.lastname@example.org.
Find out how having the right tools, plus a deep knowledge of irrigation products and of how things are typically done in one’s local area can really help a troubleshooter
A knowledge base worthy of Holmes
After decades of working in the industry, these professionals have learned about hundreds of irrigation products and their histories. They also know how installers in their area typically put things together, making them able to look at a system and tell you exactly who installed it.
“There are some companies in our area that I’ve followed long enough to know that they only use 1- or 2-inch pipe, and nothing in between,” says Clarke. “If I recognize that a system’s been built by them, I can make some pretty good guesses about it.”
He cites as a for-instance a few installers in his area that he describes as “separatists.” “These guys won’t listen to anyone,” he says. “So, I’ll see the same problems, over and over again, things that would be easy to avoid if anyone at those companies knew how to do math.”
Certain products have distinctive types of failures that are seen repeatedly in the field. “There’ve been times where a pressure problem that seems unexplainable is really just a valve malfunction,” Clarke says. “Some valves nearly always fail in the partially closed position as opposed to being stuck open. But you have to know which model valves do that particular thing.”
The troubleshooters’ toolbox
There are, indeed, some very cool tools the irrigation industry has developed to aid in troubleshooting. Companies like Greenlee, Rockford, Illinois, Armada Technologies, Caledonia, Michigan, and others make everything from multimeters and tracing probes to very advanced suites of devices. They include things that can make solenoids rapidly open and close, producing a “chattering” sound that helps in locating valves.
Underground wire and valve locators are valuable tools if you do not have an as-built drawing of the system and you need to find the wire path and the control valves. Ground fault locators can help you find wires that have been nicked or broken and are leaking current into the earth. These tools have sensitive wands that one sweeps over the earth similar to a metal detector to trace wire, find valves and locate faults.
While by no means a comprehensive list, some of the other tools irrigation technicians and contractors keep on their trucks include:
• Battery-powered reciprocating saw and extra blades for cutting through tree roots
• Clamping multimeter that reads amps, ohms, and voltage
• Pitot tubes, tees, and gauges to measure pressure
• Supply of waterproof splices