How to replace septic field lines

Written by tom raley
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How to replace septic field lines
Rent a digger wit a backhoe. (bulldozer image by Tammy Mobley from

If your septic field lines, also called drain lines, have become clogged with soil, roots or other items, it may become necessary to replace these lines. If your property allows it, it is advisable to install completely new field lines rather than rework or recover the existing lines. The tanks itself will not need to be relocated, which will reduce your cost considerably.

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Things you need

  • Backhoe
  • PVC Pipe
  • Hacksaw
  • Distribution box
  • Gravel
  • Perforated PVC pipe
  • Geotextile material
  • Rake

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  1. 1

    Layout the new field line. Make the new field lines at least as large as the old lines, although they do not have to be the exact configuration. You can change the length and number of lines to accommodate the new area as long as the total amount of field line does not diminish.

  2. 2

    Dig out the field lines and trenches with the backhoe. Dig the field lines a minimum of 60 cm (24 inches) wide and 75 cm (30 inches) deep. Excavate trenches from the head of each field line trench to a central point. From this central point dig another trench to the septic tank or to a point which intersects with the current drain line.

  3. 3

    Cut into the existing drain line and install a section of PVC pipe to start your new drain line. Add pipe as needed until you reach the point where the ditch breaks off toward each of the field lines.

  4. 4

    Install the distribution box so it is as perfectly level as possible to allow for even distribution of the waste water to the field lines. Insert the pipe from the septic tank into the inlet port. Install an exit line for each field line.

  5. 5

    Pour gravel into the field line trenches to a depth of 30 cm (12 inches) deep and rake it smooth. Lay perforated PVC pipe atop the gravel. Connect these lines coming from the distribution box using solid PVC pipe. Make certain all connections are secure and firmly in place.

  6. 6

    Pour additional gravel into the field lines until the PVC pipe is covered to a depth of 5 cm (2 inches). Rake the gravel smooth. Lay down a layer of geotextile material to prevent soil and roots from filling the gravel bed. Back-fill the trenches and field line.

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