Drip irrigation, often called trickle or micro-irrigation, delivers water directly to the plant’s root zone, making it a highly efficient watering method. This targeted approach is a significant improvement over traditional sprinkler systems, which lose substantial water to wind drift and surface evaporation. Converting an existing sprinkler line to a drip system is a practical step toward water conservation, offering typical efficiency over 90%, compared to the 50% to 75% efficiency of overhead sprays. This conversion utilizes existing underground infrastructure, allowing homeowners to reduce water waste and provide precise hydration to landscape beds, shrubs, and vegetable gardens.
Planning the Drip Layout and Water Needs
The initial planning phase requires assessing the water supply and the specific needs of the plants. The first step involves determining the available water flow rate, measured in gallons per hour (GPH), by performing a simple bucket test on the water source. This maximum GPH sets the limit for the total number of emitters that can operate simultaneously on that zone. For instance, a supply delivering 240 GPH can support 240 one-GPH emitters.
Successful drip irrigation relies on grouping plants with similar water needs onto the same zone. Trees and established shrubs require infrequent, deep watering, while annual flowers and vegetable gardens need more frequent, shallow watering. Combining these plant types on a single zone will result in either over-watering the shrubs or under-watering the vegetables. After mapping plant locations, calculate the total flow requirement for each planned zone by adding up the GPH rating of every emitter and dripline section intended for that area. This calculation ensures the total demand does not exceed the supply capacity of the converted line.
Essential Conversion Components
Converting a high-pressure sprinkler line requires a specialized set of components, known as the head assembly, to adapt the system to low-flow drip irrigation. The process begins with the conversion adapter, which threads onto the existing 1/2-inch sprinkler riser after the spray head is removed. This adapter typically converts the pipe thread to a male hose thread (MHT) connection, allowing standard drip components to be attached.
The pressure regulator is mandatory because residential sprinkler lines operate at 50 to 70 pounds per square inch (PSI), far exceeding the 10 to 30 PSI range required by drip emitters. Most residential regulators are preset to a fixed output, often 25 PSI, to ensure a consistent flow rate and prevent fittings or tubing from rupturing. Following the regulator, a filter is installed to prevent debris from clogging the tiny orifices of the drip emitters. For effective filtration, a screen with a minimum fineness of 120 mesh is recommended to block fine particles like sediment and rust.
Physical Step-by-Step Installation
Installation begins by shutting off the water supply to the entire irrigation zone at the main valve. Next, remove the existing sprinkler head from the riser, often requiring excavation to fully expose the male pipe thread (MPT) fitting. Once exposed, cap off any unused risers on that same zone to maintain pressure for the converted head.
The head assembly components are installed in sequence directly onto the exposed riser: the conversion adapter, followed by the filter, and then the pressure regulator. These connections are typically hand-tightened only, as overtightening with a wrench can damage the plastic threads and cause leaks. After the head assembly is secure, the main distribution tubing, usually 1/2-inch polyethylene, is connected to the final tubing adapter.
It is helpful to unroll the tubing and leave it in the sun for an hour or two before installation. The heat makes the material more pliable and easier to work with.
Next, the main tubing is laid out according to the design plan, secured to the ground with plastic stakes approximately every three to six feet. Branch lines, often 1/4-inch micro-tubing, are connected to the main line using small barbed fittings inserted into punched holes. The micro-tubing is run to individual plants, where a dripper or micro-sprayer is installed near the root zone. For trees or large shrubs, a loop of dripline tubing can be placed around the plant’s drip line to ensure comprehensive root saturation. The end of the main distribution line is temporarily left open before the end cap is installed.
Testing, Flushing, and Ongoing Care
Before installing the final end cap and all the emitters, it is essential to flush the main distribution line. The water supply should be turned on slowly to allow any dirt, plastic shavings, or debris introduced during installation to exit through the open end of the main line. This flushing process should continue until the water runs completely clear, which protects the small emitter orifices from clogging.
After flushing, the end cap or figure-eight clamp is secured to the main line, and the system is fully pressurized to check for leaks. All hand-tightened connections in the head assembly should be checked for weeping, and the tubing layout inspected to ensure the emitters are operating correctly.
For ongoing care, the filter screen should be regularly removed and rinsed, especially if the water source contains high sediment, to maintain the system’s intended flow rate and pressure. During the winter months in freezing climates, the system must be winterized by draining all water from the lines, removing the filter, regulator, and timer, and storing these sensitive components indoors to prevent freeze damage.