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

A broken sewer pipe under your home is a problem that can quickly become a serious—and expensive—challenge. From foul odors and slow drains to structural damage and health hazards, ignoring the problem is never a good idea. However, by understanding the basics, you may be able to fix a broken sewer pipe or make an informed decision about hiring a professional.

This step-by-step guide will show you how to identify a damaged sewer line, taking into account different types of home foundations—such as crawl spaces, and slab-on-grade. We’ll also cover modern trenchless repair methods that can save time and minimize disruption to your home.

Common Signs of a Broken Sewer Line Under Your Home

A damaged sewer line under your home can cause more than just plumbing problems—it can affect your foundation, indoor air quality, and even your health.

Here are some of the more common warning signs:

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.

If you see any of these signs, it’s important to take action. Below, we’ll explain both traditional repair methods and advanced trenchless solutions—so you can choose the approach that best suits your situation.

Understanding Your Home’s Construction Type

Before starting any repairs, it’s important to know what type of foundation your home has. The method of accessing and repairing a broken sewer pipe varies depending on the foundation.

Here’s a quick breakdown of the most common foundation types and how they affect your repair options.

Crawl Space

Homes with crawl spaces are usually elevated above the ground, leaving a narrow space (typically 1 to 3 feet high) between the bottom of the house and the ground.

What it means for repairs:

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

Slab Foundation

With a slab foundation, your home sits directly on a poured concrete slab with no open space underneath.

What this means for repairs:

• 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

Knowing your home’s foundation type helps you plan effectively, whether you’re doing the work yourself or hiring a professional.

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

Once you’ve confirmed that there is a broken sewer line under your home and understand your home’s foundation, it’s time to begin repairs. Here’s a step-by-step breakdown to guide you.

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

Digging through floors or yards to access a broken sewer pipe isn’t always ideal—or even necessary. That’s where trenchless sewer repair methods come in. These technologies enable professionals to repair or replace pipes with minimal disruption to your home’s foundation, flooring, or landscaping.

The most common trenchless options are.

1. 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

• 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

• 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

If your home has a slab foundation or limited access beneath it, trenchless repair is often the best solution. Although it’s not typically a DIY project, it can save you time and hassle while preventing long-term damage.

Knowing When to Call a Professional

While experienced DIYers can tackle some sewer pipe repairs, there are situations where calling a licensed plumber, such as Almco Plumbing, is the safest and smartest choice. Working under your home, especially with older or deeply buried sewer lines, comes with real risks and challenges that shouldn’t be underestimated.

Here are some signs that it’s time to bring in a professional:

• 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.

Even if you’re comfortable with minor plumbing work, sewer line repairs, especially those under your home, are a different level of complexity. In many cases, the cost of professional service is well worth the time, safety, and peace of mind it provides.

The most important thing, whether you choose a traditional or trenchless approach, is to restore your home’s plumbing system reliably and safely.