Underground irrigation lines deliver water directly to landscape plants, making watering efficient and automated. Successful installation requires careful design to ensure proper water distribution and system longevity. Running these lines requires a methodical approach, beginning with conceptual planning and material selection, followed by preparing the ground, laying the pipes, and connecting the final components. This guide outlines the steps for a do-it-yourself installation of a yard irrigation system.
System Planning and Material Selection
The first step involves determining the available water supply, which dictates the system’s size and complexity. You must measure the static water pressure (PSI) and the water volume, or flow rate, typically expressed in gallons per minute (GPM). A simple method to find the GPM is to time how long it takes to fill a five-gallon bucket from the water source, then calculate the flow rate per minute. This maximum available GPM is a limiting factor, determining how many sprinkler heads or emitters can operate simultaneously.
Once the flow rate is established, the yard must be mapped to scale, marking the locations of the main lines, lateral lines, and water delivery devices. The system often needs to be divided into multiple zones because the total water demand will likely exceed the available GPM. Main lines, which are constantly pressurized, often utilize rigid Polyvinyl Chloride (PVC) pipe due to its high-pressure tolerance and durability. Lateral lines and drip systems, which operate at lower pressure, typically use flexible polyethylene (poly) tubing, which is easier to route around obstacles.
The choice of pipe material affects the required fittings and connectors. Rigid PVC pipe connections are permanent, requiring a chemical process using primer and solvent cement to fuse the pipe and fittings. Conversely, flexible polyethylene tubing uses barbed or compression fittings that are physically inserted into the pipe, sometimes secured with clamps. These planning details ensure the correct volume of materials is purchased and that the system is designed to operate within the limits of the home’s water supply.
Site Preparation and Trenching
Before any ground is broken, safety regulations require contacting the local utility notification center to have underground utility lines marked. This service, often accessed by dialing 811, prevents accidental strikes on gas, electric, or communication lines. Once the utility lines are clearly marked, the planned paths of the irrigation lines should be marked on the ground using flags or landscape paint. Ensure the layout avoids tree roots and other fixed obstacles.
The trenches must be excavated to the proper depth. For a typical sprinkler system, a trench depth of 8 to 12 inches is recommended to protect the pipes from lawn equipment and foot traffic. In regions with severe winter freezes, the lines should ideally be buried below the local frost line to prevent water inside the pipes from freezing and bursting them. Drip irrigation lines can often be placed in shallower trenches, sometimes as little as 6 to 8 inches deep.
Trenching can be accomplished with a shovel for smaller projects or by renting a specialized tool like a trencher or vibratory plow for larger areas. As the soil is removed, it should be placed neatly alongside the trench to facilitate easy backfilling. Maintaining a consistent depth is important for proper system drainage and for ensuring that the sprinkler heads, when installed, will sit flush with the finished grade of the lawn.
Laying and Connecting the Main Lines
With the trenches prepared, the main irrigation lines are laid out following the marked paths. For PVC pipe, cutting the pipe to length should be done with a specialized cutter to ensure a clean, straight edge. When assembling PVC, a purple primer is first applied to the pipe and the fitting to prepare the surfaces for the solvent cement. The cement is then applied, and the pipe is immediately inserted into the fitting with a quarter-turn twist to distribute the glue evenly, holding it in place for a few seconds to allow the bond to set.
Polyethylene tubing is unrolled and placed in the trench, conforming easily to curves and obstacles. Connections are made using barbed fittings or by securing the tubing to compression fittings. For main poly lines that will remain pressurized, securing the connection with two crimp rings or clamps is recommended to provide redundancy against potential leaks.
The main line must be connected to the home’s water source, which can be done by tapping into an existing outdoor faucet or directly into the main service line. Connecting to a faucet is simpler, while tapping the main line requires shutting off the water supply and cutting into the existing plumbing. A backflow prevention device must be installed immediately downstream to protect the domestic water supply from contamination. Finally, a manifold is constructed, typically using PVC, which houses the zone control valves that regulate water flow to each section of the yard.
Installing Emitters and Testing the System
The final components of the system are installed after the main lines are in place. For a sprinkler system, this involves attaching the heads to the lateral lines using risers or flexible swing pipe, often called “funny pipe.” This flexible connection absorbs stress from ground movement and makes it easier to position the head precisely at the soil surface. In a drip irrigation system, a specialized punch tool is used to create small holes in the polyethylene tubing, into which the individual drip emitters or micro-tubing feeder lines are inserted.
Before installing the final heads and emitters, the entire system must be flushed to remove debris such as dirt or plastic shavings. Water is turned on briefly to allow it to rush out of the open ends of the lines, which prevents clogging of the new components. Once the system is flushed and the heads and emitters are installed, the water is pressurized for a final check.
A thorough inspection for leaks at all fittings and connections is required. The sprinkler heads should be adjusted to ensure they are covering the intended areas and avoiding overspray onto pavement or structures. Once the system is confirmed to be leak-free and operating correctly, the trenches can be carefully backfilled with the excavated soil, compacting it gently to avoid damaging the pipes.