An automatic sprinkler system offers a precise method for maintaining a healthy landscape by delivering water where and when it is needed. Installing a permanent, underground system requires careful planning before any physical work begins. The project moves sequentially from conceptual design to component selection, and finally to the physical and electrical installation, ensuring the finished system is efficient and provides uniform water distribution.
System Planning and Zoning
The first step in designing an effective irrigation system is quantifying your home’s available water supply. This requires measuring static water pressure (PSI) and the available flow rate (GPM). Water pressure is measured by attaching a pressure gauge directly to an outdoor faucet while all other water usage is temporarily halted.
The flow rate is calculated using the simple bucket test, timing how long it takes to fill a container of a known volume, such as a five-gallon bucket. The calculation is 300 divided by the time in seconds it took to fill the bucket, which yields the GPM. This GPM figure represents the maximum amount of water the entire system can use.
The maximum flow rate dictates how the landscape must be divided into separate irrigation zones. Since the available flow cannot run all heads simultaneously, each zone must be designed so the total GPM demand does not exceed 80-90% of your home’s total GPM capacity. A typical rotor head requires more GPM than a spray head, meaning a zone with rotors will contain significantly fewer heads.
The physical layout of the heads must adhere to the principle of head-to-head coverage for uniform watering. This means the spray from one sprinkler head must reach the location of the adjacent sprinkler head to prevent dry spots. This design ensures water is distributed evenly across the entire area, leading to a healthier lawn.
Component Selection and Layout
Choosing the correct components involves matching the hardware to the hydraulic plan developed during zoning. The central control unit, or timer, can be a traditional model operating on a fixed schedule, or a smart controller that connects to Wi-Fi. Smart controllers use local weather data (ET data) to automatically adjust watering times, which significantly reduces water consumption.
Pipe material selection typically falls between rigid Polyvinyl Chloride (PVC) and flexible Polyethylene (Poly) pipe. PVC is strong, suited for high-pressure main lines, and requires solvent welding for connections. Poly pipe is more flexible, comes in continuous rolls, and is easier to install using simple compression or barbed fittings.
The system requires a backflow prevention device, a regulatory mandate designed to protect the potable water supply from contamination by preventing backflow. A common type is the Pressure Vacuum Breaker (PVB), which must be installed before the first zone valve and 6 to 12 inches higher than the highest sprinkler head. The electric zone valves, controlled by the timer, are typically grouped together in a valve box to form a manifold, simplifying installation and maintenance.
Different areas require different sprinkler heads. Rotor heads deliver water in a rotating stream suitable for large open lawns, using higher GPM over a longer run time. Fixed spray heads are better for small, irregularly shaped areas and operate for shorter periods due to their higher precipitation rate. This mixed approach allows for efficient watering across diverse landscape features.
Physical Installation of Piping and Heads
Physical installation begins by clearly marking the trenches and the exact location of all sprinkler heads and the valve manifold on the ground. Trenches should be dug 8 to 12 inches deep to protect the pipes from surface damage and temperature changes. In regions with freezing winters, the depth must extend below the local frost line to prevent pipe damage.
The connection to the main water supply (the tie-in) must be completed after shutting off the water at the meter. For the connection, a section of the existing service pipe is cut and a tee fitting is installed, followed immediately by a dedicated shut-off valve for the irrigation system. This valve allows the sprinkler system to be serviced without interrupting the home’s water supply.
The pipe is laid in the trenches, starting from the main line tie-in, running to the valve manifold, and then extending to the lateral lines for each zone. PVC sections are joined using primer and solvent cement, which chemically fuses the pipe and fitting into a watertight bond. Poly pipe connections are made with barbed fittings secured by stainless steel clamps or specialized push-fit connectors.
Once the main and lateral lines are laid, the final step before installing the heads is a thorough flush test. This involves turning on the water to each zone to purge the lines of any debris introduced during installation. After the flush, a riser is installed at each designated head location, and the sprinkler head is attached, ensuring the top of the head is flush with the final grade of the soil.
Wiring and Controller Programming
The electrical phase involves running low-voltage wiring from the controller to the valves, which are typically powered by a 24-volt alternating current (VAC) signal. The wiring is usually 18-gauge direct burial cable, run in the same trenches as the pipe and buried 6 to 18 inches deep for protection. Voltage drop is a concern over long distances, so thicker 16- or 14-gauge wire may be required for long wire runs.
The electrical circuit requires two connections at each solenoid valve: a common wire and a zone wire. The common wire (generally white, connected to the “C” or “Com” terminal) acts as the shared return path and must be spliced to one lead from every solenoid. The remaining wire lead from each solenoid is the unique zone wire, which connects to its corresponding numbered terminal on the controller.
All wire splices, especially those inside the valve box, must use waterproof, gel-filled wire nuts to prevent corrosion and short circuits. Once the controller is mounted and wired, the final step is programming the initial watering schedule. The best practice for turf grass is to water infrequently but deeply (two or three days per week), with the start time set for the early morning hours before 10 a.m.
Initial run times should be set based on the type of heads in the zone: spray heads run for a shorter duration (5 to 10 minutes), and rotors run longer (20 to 30 minutes). The system is then tested zone-by-zone, making final adjustments to the head spray patterns using a small screwdriver or specialized tool to fine-tune the radius and arc. This adjustment ensures efficient coverage and avoids watering sidewalks or driveways.