How to Replace Septic Lateral Lines

Stephen Hasty

After a septic tank anaerobically treats septic waste, the waste water flows through a supply pipe to the lateral lines. The lateral lines then disperse waste water into the rock bed of the drain-field through perforations in the bottom of the pipe.

Distribution lateral lines keep a septic system working.

Suspended solids and other material can form a sludge in the lateral lines and plug the perforations. Septic system maintenance companies clean these lateral lines with high-pressure water inserted into the pipe through a hose. The high-pressure water scours the walls of the pipe and removes the sludge buildup. Broken lateral lines are caused by freezing or being driven over. Lateral lines that are broken, or are not able to be cleaned effectively or economically, will require replacement.


Place small amounts of soil onto the Geo-textile fabric before backfilling to keep the fabric from shifting.


Use only tracked vehicles and equipment on top of drain-fields.

  1. Remove the topsoil from the rock bed of the drain-field using an excavator.

  2. Pull the existing Geo-textile fabric off the top of the rock bed being careful to keep the topsoil out of the rock layer.

  3. Dispose of the Geo-textile fabric in a municipal debris dumpster.

  4. Locate where the supply pipe attaches to the existing lateral lines in the rock bed and cut the pipe with a PVC saw.

  5. Record the elevation of the lateral pipes with the laser level.

  6. Remove the lateral pipes from the rock bed and dispose of them in a municipal debris dumpster.

  7. Shovel trenches into the rock bed so the elevation of the new pipe will match the original pipe.

  8. Lay the perforated pipe in the rock trenches so that the perforations are pointing downward.

  9. Clean the supply pipe and new lateral pipe with PVC primer.

  10. Coat the supply pipe and new lateral pipe with PVC cement and press together. Twist the pipe ΒΌ inch and then hold the pipe in place for 30 seconds.

  11. Shovel the drain-field rock around and on top of the newly installed perforated pipe.

  12. Unroll the new Geo-textile fabric onto the rock bed. Install the fabric only on the top, not the sides of the rock bed.

  13. Spread topsoil over excavated are using a tracked skid-steer. Mound the soil over the drain-field to repel surface water.