How to Repair a Sewer Pipe Under a Concrete Slab

Dealing with a damaged sewer pipe under a concrete slab can be daunting for homeowners. Traditionally, this repair would involve extensive excavation, which can be time-consuming and expensive. However, modern techniques now allow for less invasive solutions. This article will explore an innovative method to repair sewer pipes without breaking through your home’s foundation. This Old House plumbing and heating expert Richard Trethewey demonstrates a cutting-edge technique to rescue a buried, root-clogged pipe without extensive digging.

Understanding the Problem With Repairing a Sewer Pipe

Before diving into the repair process, you’ll want to understand the root of the issue. Sewer pipes under concrete slabs can deteriorate over time due to various factors, such as the corrosion, cracks or breaks from shifting soil, and even tree root intrusion. All of these problems can lead to sewage backup, foul odors, and potential health hazards.

Sewer Pipe Diagnostic Inspection

The initial phase of repairing a sewer pipe under a concrete slab involves a thorough inspection. 

Video Inspection

A video inspection is the most effective way to examine the interior of the sewer pipe. Here’s how it’s typically conducted:

1. Insert a snake attached with a high-quality video camera and a bright light into the sewer pipe—these are expensive but can be purchased at major home improvement stores or online retailers.
2. Slowly feed the camera through the pipe, carefully observing the interior condition.
3. Look for signs of damage such as cracks, tree root intrusion, or pipe misalignment.
4. Record the inspection for further analysis and to pinpoint the exact location of issues.

In the video, Richard Trethewey and his team use this method to identify root intrusion at several pipe joints, demonstrating the effectiveness of video inspection in diagnosing sewer pipe problems.

Assessing the Damage

Once the video inspection is complete, professionals can determine the best course of action. They consider factors such as:

• The extent of root intrusion
• The overall condition of the pipe
• The location and severity of any cracks or breaks
• The potential for future issues based on the current state of the pipe

This assessment helps in deciding whether a full pipe replacement is necessary or if a less invasive repair method, like pipe lining, would suffice.

Preparing for Sewer Repair

Before the actual repair process begins, some preparatory steps are necessary for a smooth and effective job.

Clearing the Pipe

The first step in preparing the pipe for repair is to clear it of any obstructions:

1. Use a specialized drain snake with a cutter head attachment.
2. Feed the snake into the pipe and activate its motor.
3. The spinning cutter head removes tree roots and other debris from the pipe’s interior.
4. Thoroughly clean the pipe to create a smooth surface for the new lining.

Mixing the Epoxy

The next step involves preparing the epoxy that will form the new pipe lining:

1. Mix a two-part epoxy in a clean bucket.
2. Use an electric drill with a mixing paddle for thorough blending.
3. Ensure the epoxy is well-mixed and ready for application within its working time.

Richard Trethewey emphasizes the importance of working quickly once the epoxy is mixed, as it begins to set within 45 minutes.

The Sewer Pipe Lining Process

The pipe lining technique demonstrated in the video offers a non-invasive solution to sewer pipe repair. This method creates a new pipe within the existing one, effectively sealing off any damage without the need for extensive excavation.

Preparing the Liner

The first step in the process involves preparing the polyester liner:

1. Lay out the polyester sock-like liner.
2. Use a traffic cone as a funnel to pour the mixed epoxy into the liner.
3. Feed the epoxy-filled liner through steel rollers to evenly distribute the resin.

Installing the Liner

Here is how Richard set the liner:

1. Attach the prepared liner to a two-part air chamber.
2. Use compressed air to invert the liner as it’s fed into the existing pipe.
3. The inversion process turns the liner inside out, pressing the epoxy-coated side against the old pipe’s interior.

This technique ensures that the new lining adheres perfectly to the existing pipe, creating a seamless repair.

Curing the Liner

After installation, the liner needs to be properly cured to form a solid, durable pipe:

1. Insert an inflatable rubber bladder into the newly installed liner.
2. Fill the bladder with cold water to expand it, pressing the liner firmly against the old pipe.
3. Allow approximately two hours for the epoxy to cure and harden.
4. Once cured, drain the water and remove the bladder.

The result is a smooth, jointless pipe that effectively seals off any previous damage or root intrusion points.

Benefits of Trenchless Sewer Pipe Repair

This method of repairing sewer pipes offers several advantages over traditional excavation techniques:

• Elimination of root intrusion points
• Improved pipe performance and longevity
• Lower overall cost compared to full pipe replacement
• Minimal disruption to your property
• Significantly reduced repair time

When to Consider Professional Help for a Sewer Pipe

While the trenchless repair method is less invasive than traditional techniques, it still requires specialized equipment and expertise. Homeowners should consider professional help when:

• Multiple drain lines in the home are backing up
• Persistent foul odors are around drains or in the yard
• Sinkholes or wet spots appear in the yard
• There is a noticeable decrease in water pressure or drain flow

Professional plumbers have the tools and knowledge to accurately diagnose the problem and implement the most effective solution.

Future Maintenance for Your Sewer Pipe

Preventive maintenance can help extend the lifespan of your sewer line and avoid recurring issues. Here are some tips for homeowners:

• Regular Inspections: Schedule an annual video inspection to monitor pipe conditions.
• Tree Root Management: Consider removing or managing trees close to sewer lines to prevent root intrusion.
• Proper Waste Disposal: Avoid flushing non-degradable items and dispose of grease properly to reduce buildup in the pipes.

By staying proactive, you can save money and prevent serious plumbing problems down the road.

Our Conclusion

Repairing a sewer pipe under a concrete slab no longer requires extensive excavation and disruption. The trenchless pipe lining method offers an efficient, cost-effective solution that can restore your sewer line to full functionality with minimal impact on your property. While it requires specialized equipment and expertise, this innovative technique represents a significant advancement in plumbing repair technology.