Know where your sprinkler's water pipe goes before you dig.

How Deep Are Sprinkler System Water Lines in the Ground?

by Athena Hessong

One of the best ways to save time maintaining your yard is to have an automatic sprinkler system installed. These systems have buried pipes that carry water to sprinkler heads. The depth these water lines is important to know because you don't want an adult or a child digging in the yard to strike a water line accidentally. It also is important to avoid having the water line too close to tree roots or buried utilities.

Type of Pipe

The type of pipe used for your sprinkler system's water lines will likely be PVC. This sturdy piping has a rigid structure to keep it from being compressed by the soil. If you are digging in your yard and notice a white or blue PVC pipe, it is likely feeding your sprinkler system. For most lawns, a 3/4- or 1-inch-wide water line should provide adequate pressure for a sprinkler system.

How Deep Are the Lines

The depth of water lines varies by the installer, but expect them to be between 8 and 10 inches below ground. At this depth, they are within the root zone for most grasses, which is between 6 and 12 inches down. This depth also helps to protect the system from light freezes that might cause problems at shallower depths. However, if you live in a region that experiences long freezes in winter, it is a good idea to drain the sprinkler system of water regardless of the pipes' depth.

Trenching Into the Ground

During the installation of the sprinkler system, you or the installers will dig deep trenches in your yard to lay down the pipes. With a typical width of 4 inches, these trenches pose a hazard in your yard. Keep children and pets away from the trenches until you fill them after the pipes are in place.

Finding Sprinkler Water Lines

If you already have a sprinkler system in your yard, look at the location of the sprinkler heads; the buried water line should run in a straight line between them. The sprinkler heads come off the main water line at right angles on risers, which are short pieces of pipe that meet the sprinkler head at the soil surface. Avoid digging below 8 inches near water lines to avoid damaging your sprinkler system. If you must have a flower bed or vegetable garden across an area where a sprinkler water supply pipe runs, build a raised bed, which does not require digging. Be sure you don't cover any sprinkler heads if you install a raised bed.

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