How Wide to Trench for Sprinklers

Climate

• Where you live has a lot to do with how you should trench out the lines for your sprinklers. Cold climates where the temperatures frequently dip below freezing in the winter call for larger trenches in general because the deeper your trench is, the less likely the lines will freeze. Make your trench at least 18 inches in cold environments. More mild climates call for a trench that's about 8 to 12 inches.

Sprinkler Types

• Sprinkler trenches should also be dictated by how wide and tall your sprinkler heads are. If you are using standard 4-inch pop-up sprinklers, for example, your trench doesn't need extra space on the sides to accommodate the sprinklers. However, installing a large impact sprinkler will require you to make the trench at least as wide as the sprinkler body. Measure the circumference of the sprinkler body, and add 2 inches to find the proper trench size.

Pipe Size

• Most sprinkler pipes are no larger than 3/4 inches, so the trench doesn't have to be very large to accommodate the pipe. As a general rule, you should make your trench at least 2 inches wider than the size of the pipe to ensure the pipe sits firmly into the hole. If your sprinkler pipe is 1 inch, for example, make the trench at least 3 inches wide to accommodate the larger pipe, which is the bare minimum required to lay your pipe correctly.

Operating Room

• While a sprinkler trench only needs to be a couple of inches wider than the pipe itself, you should consider how much work you will be doing within the trench. If you are preassembling the sprinklers above ground, the trench doesn't need extra room to accommodate your hands and tools. But if you plan on installing couplers or sprinkler heads below ground, you should add 5 inches to the width of the trench. The extra space can come in handy when working in tight spaces.