By Geoff Connellan
In an ideal world, the only maintenance required to keep a turf and landscape irrigation system functioning optimally would be planned or preventative maintenance. The reality is that things happen.
The systems consist of many moving and vulnerable parts that are prone to wear and malfunction, if not looked after. The operating environment for irrigation systems is harsh. They can be subjected to electric shock, flooding, pressure surges, chemical attack, storm damage, kicked, eaten and vandalized. Irrigation systems need to be cared for and nurtured.
Overview of preventative and reactive maintenance
Maintenance can be considered in two ways:
- Preventative maintenance — The work carried out on equipment to ensure that it is functioning correctly with the aim of avoiding future breakdown or malfunction. It is planned, conducted regularly, and carried out to a schedule. It is not just about minimizing the occurrence of faults; it is about keeping equipment functioning at optimum levels and also achieving more effective and efficient use of water. Benefits including extended service life and lower operating costs should be outcomes of a good preventative maintenance program.
- Reactive maintenance — Responding to breakdowns and unplanned malfunctions that occur during the irrigation season, without notice, is reactive maintenance. Fixing leaks, broken pipes and faulty solenoid valves is reactive maintenance. It can be expensive, as the call-out time is at short notice.
Components of a pressurized irrigation system
The maintenance demands of an irrigation system depend upon the type and characteristics of the equipment installed and the environment in which it operates. The core/key elements of a pressurized system are/include:
- Pumping plant — including suction, intake, outlet, pump, motor, power supply and pump controller
- Filtration system
- Water treatment system
- Pipe network mainline, sub-main, lateral
- Hydraulic regulation valves — isolation, pressure, flow, air release
- Controller and communications system.
- Sensors — rain, soil moisture, flow
- Automatic remote control valves (solenoid valves)
- Driplines and drip emitters including flushing and air release devices
The degree of maintenance, both in terms of resources and timing, varies with each part of the total system. Some components, if well designed — such as pipelines and pumping plants — can provide many years of service with low maintenance input. Other components, such as sprinklers, tend to require significant amounts of maintenance on a reasonably frequent basis in order to achieve optimum performance.
Subsystems: hydraulic and electrical
An irrigation system can be considered to be composed of two subsystems, hydraulic and electrical. An understanding of each of these is required to be able to assess the functioning of equipment and provide competent maintenance.
The hydraulic side includes understanding the theory of water flow in pipes, friction loss, pump duty, pressure regulation and hydraulic operation of components.
The electrical side includes understanding the theory of electrical power, transformers, voltage, current, resistance and signal communications.
Both of these subsystems behave according to set rules. By applying simple tests and measurements, it is common to be able to quickly determine the nature and source of a fault.
The tools required to carry out these tests are relatively simple and inexpensive, including volt/amp meters, pressure gauges and flow meters.
Understanding each of these subsystems provides a solid foundation for the maintenance of irrigation systems.
Risks to irrigation systems
Unfortunately, there are many circumstances that can give rise to faults or ineffective operation of an irrigation system. A key issue is the environment in which these systems operate. Both the above ground and below ground are potentially hazardous.
Above-ground risks may be due to adverse weather conditions of electrical storms, wind storms and flooding.
Below-ground conditions, including dampness, result in corrosion of connectors, flooded communication components, soil-borne pests/vermin, root intrusion and rocks. Below ground is also subject to electrical damage from lightning, especially decoder systems.
People are also a risk, with interference to the operation of systems and in some cases deliberate vandalism.
Water quality is becoming an increasing risk. As the level of use of lower-quality water increases, so does the potential for malfunction of components. There are also potential health risks to people and the environment.
Some parts of an irrigation system are likely to require more maintenance than others due to the function and complexity of the equipment or device, the operating environment and the number of units in use.
Some examples of items that are prone to higher levels of maintenance include:
- Multiple units — e.g. 50 to 80 heads on a sports ground
- Stream trajectory sensitive to nozzle size, nozzle condition, hydraulic operating conditions
- Water distribution sensitive to installed position; depth and vertical alignment
- Soil environment — sand/debris may interfere with rotation and distribution or wear seals
- External loads and stresses — reduce effectiveness
- Diaphragm operation sensitive to internal port blockage (water quality)
- Low voltage supply/power (24 V AC) is vulnerable to small voltage drops
- Electrical connections in harsh soil environment
- Function dependent on two subsystems of electrical and hydraulic
- Numerous units in the field
- Multiple units — hundreds/thousands
- Small pathways — blockage
- External loads and stresses — tubing interfered with or damaged
- Dripline tubing connections vulnerable
Preventative maintenance programs
The overall objective should be to have in place a sound preventative maintenance program that reduces the need for unscheduled service during the irrigation season.
A preventative maintenance program should include the mechanical and electrical components, as well as the hydraulic and water application performance of the system.
The main items to be included are:
- Pump — Electrical power consumption and condition; mechanical, e.g. bearings; hydraulic e.g. flow and pressure
- Filter — Debris; flushing; flow, pressure loss
- Controller — Programs suited to site; voltage output, earth protection systems
- Wiring — Resistance of circuits, including connectors; evidence of deterioration
- Sensors — Operation and controller response; sensor calibration
- Pressure regulation — Settings; pressure check
- Flow monitoring — Output signal; display and recording
- Valves — Operation; Opening and closing
- Piping and joins — Leakage
- Sprinklers — All heads operation; condition and delivery performance
- Drip emitters — Delivery rate; blockage; application position
- Drip tubing — Connections; wetting pattern
Many systems will have specialized equipment, such as water treatment systems that will have their own requirements.
The pressures and stresses arising from the freezing of water are readily capable of fracturing pipes and breaking fittings. Removal of all of the water from irrigation systems is an important precaution in freezing climate areas.
Expulsion of water by air or draining of water from the system is a preventative maintenance program.
Details on the procedures for winterization are provided by irrigation companies.
Sprinkler head condition assessment
The operation and condition of each sprinkler/rotor should be regularly checked. The following are fault categories that can be identified.
(1) Rotation — Not rotating to desired degree (continuous 360 degrees for full-circle sprinkler); slow rotation; no rotation
(2) Damaged — Wiper seal damaged/broken; turret seals leaking; rubber top damaged/removed; riser stem damaged/broken; nozzle damaged/broken
(3) Vertical alignment — Riser stem “tilt” or angle affecting performance of sprinkler
(4) Clearance — Riser stem not clearing surrounding ground/turf, due to sprinkler too low in ground
(5) Grass obstruction — Grass/turf interfering with nozzle stream (clearance would be good if grass height was maintained)
(6) Arc adjustment — Part-circle sprinklers over-spraying outside of target area
Drip system maintenance
The risk of malfunction of drip systems is well recognized, and preventative maintenance programs are strongly promoted.
These programs are mainly designed to prevent blockages of emitters. They include a) flushing of the system, b) chemical injection, and c) scheduling of irrigation.
Over time, debris can lodge in the drip system pipe and valve network and, in some cases, organic material can grow within the pipes. Deposits and growth can build up on the walls of the pipes.
Flushing of the complete network at velocities greater than the system design velocity facilitates removal of these contaminants.
The chemicals that may be injected into a drip system include fertilizers, disinfectants, pH modifiers and chemicals to protect the drip system through dissolving particles.
Chemical injection requires precision hydraulic management. Preparation and adjustment of correct concentrations is a fundamental part of achieving effective control and outcomes that are safe for humans and the environment.
One of the risks associated with drip systems, particularly where the emitters are buried, is the intrusion of roots into the emitter and pipe. Also, there is the risk of soil particles being drawn back (sucked back) into the pipes.
The risk of root intrusion occurring can be mitigated through the management of the irrigation application. Operating the irrigation so that the plants/crop are not excessively stressed will reduce the likelihood of root build-up close to the emitters.
Monitoring of soil moisture, using sensors, will also provide information about the appropriate/threshold set point value to initiate irrigation. The use of emitters that incorporate some form of herbicide (e.g. Treflurian) or copper will minimize the risk.
If the soil around the emitter pipe is saturated, and water is drained from the system network or line, there is a chance that soil debris may be drawn back into the pipe. Other than avoiding over-watering, emitter design that withstands suck-back can be used.
Troubleshooting is part of reactive maintenance. A fault, malfunction or poor performance has been identified and it needs to be corrected.
A systematic approach is required, as in many cases there are multiple factors contributing to the fault. Following a logical and thorough progression of tests will ensure that the primary cause or causes are identified.
Many manufacturers of irrigation, pumping and water treatment equipment provide troubleshooting guides for their equipment. Diagnostic facilities on controllers, pumps and irrigation system are valuable in identifying suspect components.
Strategies to reduce reactive maintenance
Through good design, careful installation and smart management of the irrigation system, the need for reactive maintenance can be reduced.
Industry guidelines — including the Landscape Irrigation Best Management Practices, authored by Irrigation Association & American Society of Irrigation Consultants (2014) — provide comprehensive information on all aspects of irrigation system design, installation and management.
Reliability and robustness should be built into the irrigation system at the design and equipment-selection stages.
Dollar savings on lower-quality specified equipment will generally end up costing more in the long term, and will certainly lead to high reactive maintenance costs.
In addition to the hardware issues, there is site irrigation performance to be considered. Lower application uniformities not only result in increased water costs, but also increased costs of turf surface maintenance and repair.
A key risk is the loss of controller programming and archival performance data. Having backup for irrigation controller settings is a logical protection strategy. However, the backup needs to be secure and off-site, either physically or in the Cloud.
Total loss of a PC from meltdown, electrical shock or flooding is not uncommon. There is also the possibility of theft. In many situations, the irrigation system is considered incidental to the organization’s assets.
The investment in irrigation infrastructure is large. Individual components — in particular high-tech components — are expensive, and there are often multiple systems installed.
Knowing the details and locations of all of these assets is essential for an organization. They should be included with all other assets.
Making provisions for depreciation and also being covered under the organization’s insurance policies is sound management.
Having adequate insurance to cover loss of equipment is part of risk minimization. Provision needs to be made not only for the hardware and software, but also the time required to re-install replacement equipment.
Through good design and selection of quality components, the reliability of irrigation systems can be enhanced. However, some maintenance is required on all physical systems to keep them in good working order.
In addition to the periodic checks recommended by manufacturers, it is valuable to identify the risk areas and potential weak spots in the system. These risk areas require special attention and should be included as part of a preventative maintenance program.
While preventative maintenance is often considered to only involve the physical parts (equipment) of the system, conducting regular inspections of the system water application performance, including audits, is a good investment.
Conducting regular audits of the performance of the irrigation system, including uniformity and precipitation rates, not only contributes to the efficiency of the irrigation but also provides valuable information about the overall status of the system and points of weakness.
Possessing the capacity to carry out maintenance to the required standard is essential. In addition to the appropriate skills, being equipped with comprehensive up-to-date information, including plans and manuals, is important.
It is also important to learn from maintenance experiences, both the planned and unplanned events. Recording fault events, work done and test results provides a sound basis for the development of a quality preventative maintenance program.
The key message is that preventative maintenance should be carried out prior to the commencement of the irrigation season, with the aim of reducing the need for reactive maintenance.
Geoff Connellan is principal at G & M Connellan Consulting. He has 30 years’ experience in urban horticultural water management, research and education. His expertise includes water sources, water demand management, evaluation of water use, irrigation technologies and strategies for sustainable irrigated open space. He has provided water management advice on numerous significant turf and landscape sites around Australia. He is the initiator and project manager of the SmartGardenWatering.org.au website, and was awarded the MacLean Iedema Award in recognition for his outstanding contribution to irrigation in Australia.
Connellan is author of Water Use Efficiency for Irrigated Turf and Landscape, which provides a logical and scientifically sound approach to irrigation in urban areas. It is based on green space delivering defined outcomes using the principles of water sensitive urban design and irrigation efficiency. The book covers all stages of the water pathway — from the source to delivery into the plant root zone. Major topics include system planning, estimating water demand, water quality, irrigation systems, soil management and irrigation performance evaluation. For more information, visit http://www.publish.csiro.au/pid/5263.htm