An irrigation “zone” refers to a specific grouping of sprinkler heads that are all controlled simultaneously by a single automatic valve. This configuration allows for specialized watering schedules tailored to different landscape types, such as turf, flower beds, or vegetable gardens. Expanding an existing system by adding a new zone is a common project for homeowners looking to improve coverage or adjust to new landscaping designs. This guide provides a roadmap for integrating an additional watering area, covering necessary planning, plumbing work, electrical wiring, and final system programming.
Assessing System Capacity
Before any physical work begins, evaluating the existing system’s capacity is an important preparatory step. This assessment focuses on the hydraulic capacity of the water source and the electrical capacity of the controller. Exceeding the limits of the water supply will result in low pressure across all zones, significantly reducing system efficiency.
The hydraulic assessment requires estimating the necessary flow rate (GPM) for the proposed new zone. This estimate is calculated by summing the GPM ratings of all the individual sprinkler heads planned. This total GPM must be compared against the available flow rate from the main water line or pump to ensure the supply can maintain adequate pressure, typically between 30 and 50 pounds per square inch (PSI), during operation.
The second consideration involves the system’s electrical control unit. The existing sprinkler controller must have an available terminal slot specifically labeled for a new zone, often referred to as a “station” terminal. If all terminals are currently in use, a controller upgrade may be necessary before proceeding with the installation of a new valve.
Plumbing the New Valve and Sprinkler Heads
Once capacity is confirmed, the physical installation begins by turning off the water supply to the main irrigation line for safe connection. Planning the route for the new piping involves trenching a path from the existing main line to the furthest point of the new zone. Trenches generally need to be deep enough to protect the pipe from damage, often between 6 and 12 inches, depending on local climate and frost lines.
The new zone requires tapping into the existing main line, which carries pressurized water. This is typically done using a saddle tee fitting or cutting and inserting a standard PVC tee. Precision is important here, as the integrity of the main line depends on clean cuts and proper adhesion.
The remote control valve, which acts as the solenoid switch for the zone, is connected downstream of this tee connection. This valve should be housed within a protective valve box, placed in an accessible location for future maintenance. The valve assembly uses pipe primer to chemically prepare the surface, followed by PVC cement, which creates a strong, solvent-welded seal between the fittings.
From the outlet side of the valve, the new lateral line pipe is run through the prepared trench toward the sprinkler head locations. Each location requires a connection to the lateral line, usually achieved with specialized fittings like swing joints or flexible pipe risers. These connections allow for precise vertical and horizontal adjustment of the head, ensuring the spray pattern is level with the ground surface. Selecting the appropriate head type—such as spray heads for small areas or rotors for larger areas—is important for achieving efficient coverage.
Connecting the Zone to the Controller
Following the plumbing, the electrical connection to the controller must be established using low-voltage irrigation wire. This wire, typically 18-gauge direct burial cable, is run alongside the pipe in the trench from the valve box back to the main controller location. Care must be taken to avoid damaging the insulation during the backfilling process.
Within the valve box, the new valve’s solenoid has two wires that require connection to the main cable running to the controller. One wire from the solenoid connects to the common wire, which is a shared neutral path used by every zone in the system. The common wire often has a designated color, frequently white, and must be spliced with the existing common wire bundle.
The second wire from the solenoid is the dedicated power wire, often referred to as the “hot” or “zone” wire. This wire carries the 24-volt alternating current signal to activate the valve and is connected to the specific, unused terminal slot identified earlier on the controller.
All wire connections made within the valve box must use specialized waterproof connectors, such as silicone-filled wire nuts or grease caps, to prevent corrosion and short-circuiting caused by moisture exposure. Securing these connections properly ensures the long-term reliability of the solenoid activation signal.
Final Setup and Programming
With the physical and electrical components connected, the final stage involves testing and programming the new zone. The main water supply can now be fully restored, and the system should be checked for immediate leaks at all new fittings and connections. A manual test run of the new zone is initiated directly from the controller interface to confirm the solenoid activates correctly.
During this initial activation, the spray patterns of the newly installed sprinkler heads require careful adjustment. The radius and arc of each head should be set to ensure head-to-head coverage, meaning the spray from one head reaches the base of the adjacent head, providing uniform water distribution. Any minor leaks or misaligned heads must be addressed before proceeding.
The final action is programming the controller to incorporate the new zone into the regular watering schedule. This involves inputting the appropriate run time for the specific area’s needs and soil type, along with the desired start time and frequency. If the zone fails to turn on during testing, the first steps for troubleshooting involve re-checking the connection at the controller terminal and verifying the integrity of the common wire splice.