After you've planned your irrigation system layout, you can move forward with the installation, which includes digging trenches for the pipes. Choose a trench-digging method that offers you a consistent depth throughout the area. The trenches should be deep enough that you won't pierce them with routine lawn maintenance, such as core aeration.
Before You Dig
Even the best laid plans can go awry without the proper preparation. Before you begin digging the pipe trenches, call 811 so the utility companies can come mark any buried lines, such as gas and water lines. Also, call the building codes department, either city or county. Many areas have requirements for irrigation pipes that determine how deep you must bury them to follow your local ordinances.
Basic Depth Requirements
In most areas, burying the pipes 8 to 12 inches below the surface is adequate. This measurement is from the top of the pipe to the surface of the soil, which means your trenches must be slightly deeper to accommodate the pipes. For example, if you're using a pipe with a 2-inch diameter and you want it buried 10 inches below the surface, your trench must be 12 inches deep.
Although frozen pipes aren't a problem everywhere, burying pipes 10 to 12 inches deep typically keeps the pipes from freezing if an uncommon cold snap blows through. It also protects the pipes from damage from lawn equipment during routine maintenance. Aeration tools don't reach that far down, and that depth keeps the pipes safe from most shovel blades when you dig near the surface.
Tools to Use
Digging pipe trenches involves a good bit of manual labor, especially if you choose to dig the trenches by hand using a shovel. To speed the process, water the area for at least an hour two days before you plan to dig. This lets the water soak deep into the soil, softening it for you. For larger yards, rent a trencher instead of trying to tackle the project by hand. Many garden and home improvement stores rent these machines.
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