by Greg Mitchell 

This segment in our series deals with, arguably the most technically challenging job in the field of irrigation — namely, troubleshooting. Volumes could be, (and have been) written on electrical troubleshooting alone. Troubleshooting deals more with determining what to fix, than how to fix it. While there are books, seminars, flow-charts, and even videos that deal with the subject, none of these can substitute for experience. This article is no exception. However, with some basic outlines, and common scenarios, I will try to stress the importance of learning “How to think,” as opposed to “What to do.” This concept is the most important lesson
a technician can learn as he approaches the task of irrigation troubleshooting.

Years ago, one of my former employers, (and a damn good technician), put it this way as he prodded me towards attaining a new perspective: “Remember that everything is doing exactly what it is supposed to do . . . under the present set of circumstances.” Given that there are unalterable physical laws that govern both hydraulics and electricity, I knew that to be true. That perspective allowed me to approach the problem from a variety of angles. I knew then that my challenge was to determine which circumstances had been altered that would cause this particular malfunction. To this day, when I’m confronted by a particularly difficult, or frustrating troubleshooting scenario, I rely on that concept to freshen my approach.

Troubleshooting an irrigation system requires a thorough understanding of how each component of the system works, and how each affects the others. Because most irrigation systems consist of two independent subsystems, (low-voltage electrical control system, and high-pressure hydraulic piping/ valve/head system), a technician needs expertise in both electricity and hydraulics. Due to the fact that these two subsystems actually converge and interact at the solenoid control valve, an intimate knowledge of the internal valve components and their functions is also essential.

A capable technician is able to gather information (ie: take readings, perform tests, make visual observations), and then assess the information and interpret his/her findings. Ideally, this process leads to an efficient and timely solution to the problem.

Since irrigation systems are underground, and no two irrigation systems are exactly alike (tract-type installations may be an exception), and few have diagrams, or as-built plans, the task of troubleshooting becomes even more challenging. Variations of materials, (pipe/wire), varieties of components (controllers, valves, heads), and the absence of real standards for installation, tend to complicate the process even more.

However, to the seasoned troubleshooting technician, these factors define the norm. He accepts and even enjoys the challenge, and is seldom bored by his work. In fact, most troubleshooters love their jobs! Indeed, they savor wearing the hats of electricians, plumbers, detectives, and ultimately . . . heroes!

Knowledge and training are needed in order to be an effective troubleshooter. Proper tools and equipment are equally important. Naturally, experience is invaluable. Even with all that, the technical troubleshooting of an irrigation system remains an inexact science. Primarily, because the possibility of multiple factors contributing to a single observable symptom complicates the picture. This, in my opinion, is why troubleshooting flow-charts, while they are effective training tools, are not practical for useful reference in the field. They attempt to illustrate every possible combination of cause and effect, while plotting every possible pathway to every conceivable solution. This tends to confuse rather than clarify. Besides, they generally fold out like a huge world atlas map. Try doing that with wet or mud-caked hands!

One common category of troubleshooting is that of recognizing inherent inadequacy. That is,
an irrigation system which was improperly or poorly designed at the time of installation, resulting in a system that has never performed effectively. Some indications of this type scenario would be: heads obviously spaced too far apart; rotary heads and spray heads zoned together; improper or absence of backflow protection; undersized pipe; or same size pipe throughout the system.

In these cases, the landscape will generally reflect the inadequacy of the system. However, depending on how extreme the shortcomings may be, or how much rainfall may have occurred, the situation may not be immediately obvious.

The other, and most common, category of troubleshooting would be actual malfunctioning of an otherwise effective sprinkler system. Of course, the malfunction can be as simple as a nozzle missing from a pop-up spray head. For example, the observable symptom: geyser in lawn area while one zone is running; the indicative symptom: overall stress in turf throughout this zone, except one very green wet area near one head. This type of malfunction is a simple one that requires little technical expertise. The observable symptom offers evidence of a quick and easy solution . . . replace the missing nozzle. Let’s talk about a more elusive cause and effect — that of multiple factors contributing to a single observable symptom.

Let’s say that we test, observe and inspect a six-zone residential lawn sprinkler system. As we perform the walk-through, by activating and inspecting each station in running mode, we notice a problem on one zone. Zone 4 appears to have very low pressure, (the rotary heads barely pop up and just sort of gurgle water out two or three feet), while zone 1, 2, 3, 5, and 6, (all spray sections), seem to perform properly.

The fact that all other zones perform well would eliminate the possibility of a problem at the source, except for one important difference . . . zone 4 is a relatively large section of eight rotary heads, while the rest of the zones are smaller spray sections, consisting of six or eight spray heads each. The larger zone of rotary heads will require more gallons per minute in order to operate properly. So, a partially open valve at the source, (in this case a PVB), could potentially be a factor.

Upon investigation, sure enough, the ball valve on the PVB has been partially closed, restricting flow and probably affecting the performance of zone 4. So, we just open the ball valve and write up an invoice, right? Hold your horses! We always re-check after repairs, even if it is obviously remedied now. Uh-oh, it’s a good thing we followed through with that re-check policy, because even though the pressure on zone 4 has improved noticeably, it’s still insufficient!

This calls for a more detailed walk-through of the entire zone, closely inspecting each head while the zone is activated, looking for any indication of leakage. Bingo! One of the farthest heads has come loose, (or someone unscrewed it) from the riser. It wasn’t obvious though (no geyser), until we were almost standing on it. Water was just flooding up from under the head, making a huge puddle in the turf, indiscernible from a distance. So after excavating, replacing the stripped riser, and re-installing, as well as backfilling around the rotary head, we are done! Well, except for that final re-test.

Upon our final (we thought), re-test we discover that again, while there is a marked and substantial increase in pressure and performance, it is still only about 75% of optimum. It looks like it’s going to be one of those days.

Once again we walk the entire section, looking for any indication of additional leakage, and find none. With that possibility eliminated, it is now time to locate control valve 4. So we connect our electronic valve-location transmitter at the controller, trace, locate, and excavate valve 4. Once disassembled, the aged and bloated rubber seal and diaphragm assembly are revealed as the final contributing factors to the poor performance of zone 4. After replacing these worn-out parts, as well as the solenoid, and making new watertight wire splices, it’s time to test again, (before backfilling, of course). This time zone 4 comes on and works like a charm!

While the previous scenario may sound contrived, it is actually not uncommon, and it helps to illustrate how there are often multiple factors contributing to poor performance. It stresses the importance of proceeding through such scenarios in a systematic way, eliminating the most obvious factors first, until arriving at the final solution. It also emphasizes the importance of re-testing after completing repairs, and not relying on assumptions.

In fact, it would be wise at this point to test the zone on and off several times, in case other heads, unaccustomed to the sudden increase in pressure, should fail. This too, is a common occurrence shortly after such a repair.

When troubleshooting the electrical control system, another set of skills and strategies must be utilized. Again, the technician must rely on his knowledge, experience, and a systematic approach in order to proceed effectively. However, we will cover this at a later date.

Why, then, can troubleshooting seem so complicated? To illustrate the intricate interactions of various components and subsystems, I will list some different observable symptom categories, along with related combinations of possible causes.

Entire system won’t come on:
•  water meter off
•  shut-off/isolation valve off
• master valve failing (could be solenoid or diaphragm or complete obstruction of solenoid exhaust port)
•  no power to controller
•  no power out of controller (transformer)
•  no power at master valve terminal
•  master valve wire problem (cut, bad splice, short)
•  common wire cut before first valve
• Sensor interference/open
• any combination of above

Single zone won’t come on:
• no power out at zone terminal
• cut wire (“open circuit”)
• shorted wire (“short circuit”)
• high resistance (bad splice)
• solenoid “shorted” or “open”
• diaphragm assembly failing
• solenoid exhaust port completely obstructed
• flow control on valve shut
• any combination of above

Multiple (but not all) zones won’t come on:
• no power out on multiple terminals at controller
• cut wires, damaged wires, shorted wires, bad splices, or bad common on one “leg” of control wiring
• multiple failing solenoids
• multiple failing diaphragm assemblies
• multiple valve flow controls closed (unlikely, but not impossible)
• any combination of above.

Entire system has low pressure:
• meter not fully open or partially obstructed
• isolation/backflow valve not fully open or partially obstructed
• master valve not opening completely; (flow control, diaphragm assembly, internal obstruction, partially obstructed solenoid exhaust port)
• all control valves not opening fully/flow controls turned down (highly unlikely, but possible)
• mainline leak/only during cycling if master valve in place
• any combination of above

Single zone has low pressure:
• diaphragm assembly failing
• internal obstruction in valve
• partial obstruction of solenoid exhaust port
• section line leaks (broken pipes, heads, missing nozzles, etc.)
• any combination of above

Single zone won’t go off:
• constant power to zone terminal in controller
• diaphragm assembly failing
• solenoid plunger “sticking” in activated position (debris or corrosion in solenoid)
• valve bonnet assembly leaking
• any combination of above

Single zone seeps; puddles at lowest head on zone:
• Worn, swollen diaphragm/seating assembly
• solenoid plunger not seating properly
• debris in valve
• valve bonnet leaking slightly
• valve leaking slightly internally (hairline/pinhole)
• any combination of above

Experience can lead us to consider possibilities, occasionally weighing probability and likelihood against proven facts. This can be helpful if an experienced technician has historical data, or prior knowledge of a particular system. However, troubleshooters, as a rule, should resist the temptation to skip steps in their systematic sequence in order to pursue hunches or theories. Think clearly, confirm symptoms, and make assessments and decisions based on your own observations, tests, and solid, proven, troubleshooting methods. Do not allow outside influences to muddy the waters of clear thought with conjecture.

Once again let me emphasize that the most important thing a technician can learn is “HOW TO THINK” rather than ”WHAT TO DO,” simply because there are too many variables. You have to learn the concepts, not memorize the steps. Do not rely on maps to take you where you want to go, because the pathway is constantly changing. Always think systematically, analytically, logically, and deductively. This is the type of thinking that makes the difference between the Keystone Kops and Sherlock Holmes!

Mar 2001