Damaging an underground sprinkler system is a common consequence of home improvement projects like installing a fence, building a deck, or general landscaping. Residential irrigation lines are typically shallow, often buried between 6 to 12 inches beneath the surface, making them highly susceptible to damage from a simple shovel strike. Avoiding this costly repair requires a methodical approach that prioritizes careful preparation before any soil is disturbed. Locating and marking the system can save significant expense and effort later.
Pre-Digging Research and Identification
Homeowners should first seek out existing documentation, such as property surveys or original irrigation system maps, which provide a valuable blueprint of the pipe layout. Locating the main controller box and the primary water shut-off valve is an important first step, as the system’s main line originates from this area. Services like 811, the national “Call Before You Dig” hotline, are designed to locate public utilities such as gas, electric, and sewer lines. These services do not typically mark private infrastructure like your sprinkler system, leaving the responsibility of locating those lines to the homeowner. A visual inspection can also reveal subtle clues, such as slightly raised turf lines or areas of different-colored grass that may indicate a buried pipe or wire.
Pinpointing Components and Marking the Area
Start by identifying and marking all visible components, including the circular tops of sprinkler heads and any rectangular or round green valve boxes that house the zone valves. The lines that feed the sprinkler heads, known as lateral lines, usually run in a straight path between these heads. To confirm the path of the main and lateral lines, use a slender tool like a soil probe or a long screwdriver to gently feel for the plastic pipe beneath the soil. Push the probe into the ground every few inches along the suspected route until a solid obstruction is felt at a shallow depth. Residential lines are often Polyvinyl Chloride (PVC) or polyethylene piping, which feel distinct compared to rock or compacted soil. After the components and pipe paths have been located, use brightly colored marking flags or temporary spray paint to clearly delineate their positions. Mark an area extending at least 18 inches to either side of the suspected line path. This boundary serves as a clear visual warning to anyone performing excavation work.
Safe Excavation Techniques
The actual digging must employ techniques designed to protect the plastic lines. The most effective method is “offset digging,” which involves starting the main excavation several feet away from the marked safe zone. Dig the bulk of the necessary trench or hole using power tools or large shovels only in the area clear of the marked lines. When the excavation approaches the marked 18-inch safe zone, mechanical equipment, such as trenchers or augers, must be put away. The remaining soil must be removed using only hand tools, specifically a small spade or a blunt-nosed shovel. When working directly over a suspected line, use a gentle, scraping motion parallel to the pipe’s presumed path instead of a chopping or stabbing action. Avoid using the shovel with foot pressure, as the sudden force can easily slice through the thin wall of a PVC pipe. If a pipe is exposed, gently clear the soil around it, taking care not to pry or rest heavy objects on the line until the excavation is completed.