how to fix broken drain pipe under slab

Fixing a broken drain pipe under a concrete slab can be a complex and challenging task. It typically involves excavation, pipe replacement, and concrete work. Here’s a general guide on how to fix a broken drain pipe under a slab:

Materials You May Need:

  1. Excavation equipment: Such as a backhoe, mini-excavator, or shovel.
  2. Replacement drain pipe: Typically PVC or ABS plastic pipe, depending on local plumbing codes.
  3. Pipe fittings: Including couplings, elbows, and tees as needed.
  4. Pipe adhesive or solvent: To join the pipe and fittings.
  5. Concrete mix: For repairing the slab.
  6. Safety gear: Including gloves, safety glasses, and a dust mask.
  7. Plumbing tools: Such as a pipe cutter, wrench, and tape measure.
  8. Soil or gravel: For backfilling the excavation.


  1. Locate the Break:
    • Determine the location of the broken drain pipe. This may involve inspecting the area for signs of water damage, sewer odor, or slow drainage.
  2. Prepare the Work Area:
    • Clear the area around the broken pipe and remove any obstructions, furniture, or flooring as necessary.
  3. Excavate the Area:
    • Using excavation equipment or hand tools, carefully dig a trench around the damaged section of the drain pipe. The trench should be wide enough to allow access to the pipe and deep enough to expose it. Be cautious not to damage other utilities or the foundation.
  4. Cut Out the Damaged Section:
    • Using a pipe cutter, cut out the damaged section of the drain pipe. Make clean, straight cuts to ensure a proper fit for the replacement pipe and fittings.
  5. Replace the Pipe:
    • Measure the length of the cut section and prepare a replacement pipe of the same length. Install any necessary fittings, such as couplings, elbows, or tees, to connect the new pipe to the existing plumbing.
  6. Glue the Pipe and Fittings:
    • Apply pipe adhesive or solvent to the inside of the fittings and the ends of the replacement pipe.
    • Quickly insert the pipe into the fittings, ensuring a secure and watertight connection.
  7. Backfill the Trench:
    • Carefully backfill the trench with soil or gravel, ensuring that the replacement pipe is adequately supported and sloped to maintain proper drainage.
  8. Repair the Slab:
    • Mix concrete according to the manufacturer’s instructions and use it to repair the section of the slab that was excavated. Smooth the concrete surface and allow it to cure as recommended.
  9. Test the Drain:
    • After the concrete has cured, test the repaired drain system by running water through it to ensure there are no leaks or drainage issues.
  10. Clean Up:
    • Remove any excess soil or debris from the work area and replace any flooring or fixtures that were removed.
  11. Inspect for Proper Functionality:
    • Monitor the drain system to ensure it functions correctly without any further issues.

Repairing a broken drain pipe under a slab is a complex job that may require the expertise of a licensed plumber and professional equipment. Additionally, local plumbing codes and regulations should be followed. If you’re uncomfortable with this type of repair or if the damage is extensive, it’s advisable to consult a professional plumber or contractor who specializes in slab leak repair. They will have the experience and equipment needed to handle the job safely and effectively.