Irrigation is the controlled, artificial application of water to land or soil to assist in the growth of agricultural crops and vegetation in dry areas or during periods of insufficient rainfall. The fundamental purpose of any irrigation system is to deliver water efficiently and predictably to plants to ensure their survival and optimal growth. Modern systems are highly automated, relying on an interconnected network of components that manage the timing, routing, and dispersal of the water supply. A well-designed system ensures that every plant receives the precise amount of hydration it requires.
Initiating the Watering Cycle
The operation of an automated irrigation system begins with the water source, typically a connection to a municipal water line, well, or pump station. This main connection feeds the system’s primary pipes, which are under constant pressure from the source. Before the water enters the rest of the system, it must pass through a backflow prevention device. This device is a regulatory requirement designed to protect the public drinking water supply by ensuring contaminated water cannot flow backward into the clean water source.
The mechanism that schedules and initiates the entire watering process is the irrigation controller. The controller is an electronic timer where the user programs the desired start times, watering days, and run durations for various sections of the landscape. When the programmed time arrives, the controller sends a low-voltage electrical signal, typically 24 volts AC, through wires to the field components to begin the flow of water.
The main line pipe carries the pressurized water from the source and backflow device. This main pipe remains pressurized even when the system is not actively watering, waiting for the signal from the controller. The use of a pressurized main line allows the water to be delivered instantly to any part of the landscape when commanded.
Managing Water Distribution Through Zones
The core of an efficient irrigation system is the concept of a “zone,” which is a specific, distinct area of the landscape watered by a group of emitters or sprinkler heads that operate simultaneously. An irrigation system is divided into zones because the water pressure and flow rate supplied by the source are often insufficient to run all the output devices at once. By dividing the landscape into smaller zones, the system can manage the water supply effectively, ensuring adequate pressure for proper coverage in each area.
Water flow to each zone is regulated by a solenoid valve, an electrically controlled gate that opens and closes based on the signal from the controller. The solenoid is an electromagnetic coil that, when energized by the controller’s signal, moves a plunger to release internal pressure within the valve. This pressure differential causes the valve’s diaphragm to lift, physically opening the path for water to flow into that specific zone’s piping. When the controller terminates the electrical signal, the valve’s internal spring and water pressure reset the diaphragm, closing the valve and stopping the water flow to that zone.
This zoning mechanism is used for customizing water delivery based on specific landscape needs, such as different plant types or sun exposure. For example, a lawn area requiring a high volume of water can be one zone, while a flower bed needing a slow, targeted application can be another. The controller manages the sequence, opening and closing the solenoid valves one after another to pressurize the lateral lines that feed the output devices in that particular zone.
Methods of Water Delivery
Once the water has been routed through the open solenoid valve into a zone’s lateral lines, it reaches the final stage of application through various delivery devices. These devices are carefully selected to match the water needs of the vegetation and the physical layout of the landscape. Sprinkler heads are a common delivery method, designed to mimic rainfall over a designated area.
Sprinkler Heads
Two main types of sprinkler heads are widely used: static spray heads and rotor heads. Static spray heads distribute water in a fixed pattern, covering small, irregularly shaped areas like small lawn sections or groundcover beds. Rotor heads distribute water in a single stream that rotates slowly, covering large, open turf areas with a heavier, more wind-resistant droplet. Selecting the appropriate head type is important for achieving uniform coverage and minimizing water waste.
Drip Irrigation
Drip irrigation represents a fundamentally different method, focusing on slow, targeted delivery directly to the plant root zone. This system uses specialized polyethylene tubing with built-in emitters or small drip nozzles placed near individual plants. Drip emitters release water at a very low rate, measured in gallons per hour, allowing the soil to absorb the moisture gradually without runoff or excessive evaporation. This method is highly water-efficient and is commonly used for watering shrubs, trees, and garden beds.
The Full Operational Sequence
The complete operational cycle of an irrigation system begins at the controller, where the internal clock signals the start of the scheduled program. The controller immediately sends a low-voltage electrical current along the wires to the solenoid valve assigned to the first zone. This electrical charge instantly energizes the solenoid, causing the valve to open and allowing the pressurized water from the main line to rush into the lateral pipes of Zone 1.
The sudden influx of water pressure causes the sprinkler heads to pop up or activates the drip emitters in that zone, beginning the application of water to the landscape. Once the programmed run time for that zone has elapsed, the controller cuts the electrical signal to the solenoid valve. The valve then closes, stopping the flow of water and depressurizing the lateral line, which causes the sprinkler heads to retract back into the ground.
The controller then repeats this exact sequence for the next zone in the program, cycling through all active zones one by one. This sequential operation ensures that only one zone is pressurized at a time, conserving the system’s overall water flow and pressure capacity. After the last programmed zone has finished its cycle, the controller enters a waiting state until the next scheduled start time, completing the automated delivery of water.