How to Dig a Drain Field


A drain field, often called a leach field, is an outdoor area where contaminants from a septic system are directed and allowed to be absorbed into the ground. A drain field is composed of a series of ditches into which perforated pipes have been placed. You can't dig a drain field quickly as the task involves digging about 100 yards of ditches, but if set up correctly, a drain field lasts about a decade.

Step 1

Visit your local town hall to verify whether or not you need a permit before you begin digging and if any inspections by the local health department must be completed during or after construction of the field. Inquire about the appropriate size of the field.

Step 2

Survey the area where the drain field will be, looking for signs of proper draining. There should be no pools of standing water. Don't place a drain field in an area known for flooding.

Step 3

Take a sample of the soil to the local branch of the Department of Agriculture to assess if it has a suitable ability to absorb and drain water, known as percolation rates.

Step 4

Plan the layout of the drains. The size of the drain field depends on the size of the septic tank, the percolation rates of the soil and the expected outflow from the house. Check with your local town hall for suggestions on the appropriate size of your field based on the conditions of your land, such as groundwater levels, and area weather.

Step 5

Dig the ditches parallel to one another, with a depth of four feet and at the desired length. The trenches should slope down slightly toward the end but not be so slanted that a large pool of waste will be created at the end.

Step 6

Lay a layer of gravel about 18-inches deep into the ditch. Attach a pipe to the septic tank drain with a clamp and lay the pipe onto the gravel's surface.

Step 7

Lay an additional layer of gravel about 1 inch on top of the pipe. Place a drain cloth over the gravel and replace the dirt that was removed from the trench back on top.

Tips and Warnings

  • Never place a drain field within 100 feet of edible plants, bodies of water, or a well.

Things You'll Need

  • Perforated pipes
  • Shovel
  • Gravel
  • Clamps
  • Drain cloth


  • Drain/leach field guidelines
  • Additional drain information
Keywords: drain field, leach field, septic system

About this Author

Gail Logan is a magazine editor and freelance writer based in Atlanta, AL. She received her B.A. in Journalism from Patrick Henry College. For the past four years, she has written home design, travel and food features for national magazines, including "Coastal Living," "Texas Home and Living," "Log Home Design," and "Country's Best Log Homes." When not writing, she mentors inner-city children.

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