How to Fix a Broken Sewer Pipe Under Your House: A Step-by-Step Guide

Common Signs of a Broken Sewer Line Under Your Home

1. Sewage Smell Indoors: If you notice a strong, persistent sewage odor coming from floors, drains, or crawl spaces, it could indicate a break in the sewer line directly beneath your home.
2. Gurgling Sounds in Drains: Strange gurgling or bubbling noises when using sinks, tubs, or toilets can mean there’s air trapped in the system—often caused by a leak or blockage in the main line.
3. Frequent Drain Backups: A clogged drain may be a localized problem, but if multiple drains are backing up, especially in the lowest parts of your home, it is a strong indication of a sewer line problem.
4. Wet or Soggy Floors: A cracked pipe under a slab foundation can allow water to seep up through the floor, causing damp spots, mold growth, or even visible puddles.
5. Cracks or Shifting in the Foundation: If a sewer line leaks under the slab, it can soften the soil and cause parts of your foundation to settle unevenly, leading to cracks in the floor or walls.
6. Unexplained Pest Activity: Sewer leaks can attract rodents, gnats, and insects. If you’re seeing a sudden increase in pests with no clear source, the problem may be coming from underneath the house.

Understanding Your Home’s Construction Type

Crawl Space

Crawl Space

• Easier access to pipes without major excavation
• Allows straightforward digging and pipe replacement
• Creates good conditions for traditional repair methods

Slab Foundation

Slab Foundation

• Sewer pipes are embedded within or beneath the concrete slab
• Access often requires cutting through the slab, making repairs labor-intensive and expensive
• Trenchless methods, such as pipe lining or pipe bursting, are often preferred to avoid damaging the slab

How to Fix a Broken Sewer Pipe Step-by-Step

Step 1. Diagnose the Problem

Before you start digging or cutting into anything, take time to locate the problem:

• Look for visible signs of water damage, mold, or leaks
• If possible, use a sewer inspection camera to locate the break
• Pay attention to where the pipe runs based on the layout of your home

Consider hiring a professional for an inspection if the path of the pipe is unclear or access is limited.

Step 2. Prepare the Work Area

Safety and organization are key:

• Shut off the water supply to the affected line
• For homes with crawl spaces, remove the toilet and open the wall to reconnect the toilet vent to the existing vent inside the wall. Also, open the drywall under the sink to replace the sewer pipe running from the sink into the wall in the crawl space. The shower and bathtub can be connected to the vent within the crawl space
• Extend the cleanout outside for easier future maintenance

Mark the suspected location of the break to reduce unnecessary damage.

Step 3. Access the Pipe

How you access the broken pipe depends on your foundation type:

• Crawl Space: May require minimal digging
• Slab Foundation: Use a concrete saw or jackhammer to cut through the slab

Be careful not to damage surrounding utilities.

Step 4. Remove the Damaged Section

Once the pipe is exposed, remove the damaged section:

• Cut out the broken section with a pipe cutter or reciprocating saw
• Clean and smooth the ends of the remaining pipe to ensure a secure joint
• Properly dispose of old pipe and contaminated materials

If you have a cast iron sewer, Almco recommends replacing all existing cast iron pipes.

Step 5. Install New Pipe

With the damaged section removed, install the replacement pipe:

• Measure and cut the new pipe to length
• Use couplings and solvent adhesive (for PVC) or Husky tape (for cast iron or ABS)
• Ensure proper slope (typically 1/4 inch per foot) to allow waste to flow smoothly toward the main line

Step 6. Test the Repair

Before finishing, test the repair:

• Run water through the system and check carefully for leaks
• Inspect the repair from several access points, if possible, to ensure everything is dry and secure
• Allow adhesives or sealants to cure as recommended

Step 7. Fill & Restore

When you’re satisfied the repair is sound:

• Carefully backfill the hole, compacting the soil in layers to prevent future settlement
• Restore the concrete with an appropriate patching compound or replace flooring if indoors
• For crawl spaces, consider adding vapor barriers or insulation as needed

With the pipe repaired and the area restored, your sewer system should be back to normal. Next, we’ll take a look at trenchless repair methods—an option that can sometimes skip many of these steps altogether.

Trenchless Repair Options

1. CIPP (Cured-in-Place Pipe) Lining

CIPP (Cured-in-Place Pipe) Lining

• A flexible, resin-coated liner is inserted into the damaged pipe
• The liner is then inflated and cured using ambient conditions, warm air, or UV light to create a new pipe inside the old one
• This method is ideal for small cracks, corrosion, or damage
• It can last 50+ years if properly installed

2. Pipe Bursting

Pipe Bursting

• A new pipe is pulled through the old pipe while simultaneously breaking it apart
• This method is best suited for severely damaged or collapsed lines
• It requires access holes at both ends, but it avoids trenching through the whole length

3. Epoxy Pipe Lining

Epoxy Pipe Lining

• In this method, the interior of the existing pipe is coated with a layer of epoxy resin. After cleaning and drying the pipe, the epoxy is sprayed or poured inside and allowed to cure, forming a seamless, joint-free barrier
• It works well for minor cracks and corrosion without replacing the entire pipe
• It is best for pipes that are structurally intact but deteriorating on the inside

Knowing When to Call a Professional

Call a Licensed Plumber Such as Almco Plumbing

• Extensive Damage or Total Collapse: If the pipe is crushed, misaligned, or completely deteriorated, the job will likely require specialized tools and techniques.
• Foundation Work: Cutting into concrete slabs or dealing with structural elements requires expert handling to avoid costly mistakes.
• Unclear Pipe Layout: If you’re unsure where the pipe runs or how to access it without damaging other systems, a professional can use inspection cameras and tools to safely map everything.
• Persistent Backups After Repairs: If problems persist after what seemed like a successful repair, there may be a deeper issue requiring advanced diagnostics.
• Trenchless Repairs: These methods are not DIY-friendly. They require specific equipment, materials, and training to be done safely and correctly.

Case from Almco Plumbing: Replacing Sewer Pipes in a Home with a Crawl Space