Expanding an existing irrigation zone is a practical method to ensure uniform water distribution across a landscape, especially as plant beds mature or new areas are added. Achieving adequate coverage often requires modifying the underground network of polyvinyl chloride, or PVC, piping to install an additional sprinkler head. This process involves precise planning, careful excavation, and the solvent-welding of new components directly into the existing lateral line. Successfully integrating a new head ensures proper systemic function and prevents pressure-related issues in the overall watering pattern.
Planning the Expansion and Gathering Supplies
Determining the exact location for the new sprinkler head optimizes spray overlap and coverage. Before starting, shut off the main water supply and briefly activate the zone to depressurize the line and drain residual water. This prevents a sudden release of water when the pipe is cut.
The hydraulic capacity of the existing zone must be considered, as each head draws a specific flow rate, measured in gallons per minute (GPM). Adding too many heads can drop the operating pressure below the recommended 40 to 60 pounds per square inch (PSI), resulting in poor spray distance and inadequate water delivery. Necessary materials include a PVC pipe cutter, the appropriate size T-fitting with a threaded outlet, PVC primer and cement, a swing joint or riser assembly, and the new sprinkler head.
Excavating and Connecting the T-Fitting
Carefully excavating around the underground lateral line requires enough space to maneuver tools and fittings. A working area of at least 12 inches on either side of the planned cut location provides room for installation and necessary pipe flexion. Once exposed, the pipe must be cut squarely and cleanly, removing a section equal to the length of the T-fitting plus any required space for a slip-fix coupling, if used.
Use a ratcheting PVC cutter or fine-toothed saw for a smooth cut. Immediately remove any rough edges or burrs from both the inside and outside of the pipe ends using a utility knife or sandpaper. This deburring ensures maximum surface area for the chemical bond and prevents obstructions in water flow.
Solvent Welding
Solvent welding connects the T-fitting; the primer softens the pipe’s exterior, and the cement creates a permanent fusion. Apply primer first to both surfaces, followed immediately by a thin, even layer of cement applied to the pipe end and the fitting socket.
Insert the pipe into the T-fitting with a quarter-turn twist to evenly distribute the cement and fully engage the chemical reaction. Hold the connection firmly for approximately 30 seconds to prevent the pipe from pushing back out. Position the T-fitting with its threaded outlet facing straight upward before the cement sets rapidly. A minimum curing time of 24 hours is advised before the system is repressurized, allowing the solvent weld to achieve sufficient structural integrity.
Assembling and Adjusting the Sprinkler Head
With the T-fitting secure, install the vertical connection between the lateral line and the sprinkler head. This assembly often utilizes a flexible swing joint—a series of elbow fittings and flexible “funny pipe” tubing connected to the T-fitting’s threaded port. The swing joint provides resilience against damage from lawn equipment or ground settling, absorbing impact without stressing the rigid PVC connection.
All threaded connections require a sealing agent, such as Teflon tape or pipe dope, to prevent leaks. Wrap the tape clockwise around the male threads to ensure it tightens and seals upon installation. The swing joint or riser is then threaded into the T-fitting and connected to the base of the new sprinkler head.
Final placement involves adjusting the assembly so the top of the sprinkler head is vertical and flush with the finished grade of the landscape. This height setting is important for performance, ensuring the spray pattern is unimpeded by surrounding turf or soil. The flexible nature of the swing joint permits small lateral or vertical corrections without needing to dig up the main pipe again.
System Activation and Leak Testing
Once the T-fitting’s cement has fully cured, restore the main water supply very slowly to gradually repressurize the line and prevent a pressure surge. Cycle the irrigation zone on to activate the new head and begin leak testing. Pay immediate attention to the new T-fitting and the threaded connections of the riser assembly for any visible drips or sprays.
If no leaks are present, observe the functional performance of the new sprinkler head. Adjust the arc (pattern of coverage) and the radius (distance of throw) according to manufacturer’s specifications to match the required coverage area. The sprinkler head typically has adjustment screws that modify the trajectory and throw. After confirming the assembly is leak-free and properly adjusted, carefully backfill the trench using soft, rock-free dirt immediately around the pipe to prevent damage.