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How to Replace Sewer Line Under the House
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Blog 04/25/19

How to Replace Sewer Line Under the House

How Do Residential Drains Work?

Although the toilet and plumbing applications have been around since before Egyptian times, indoor plumbing that we enjoy now has not been around that long. With indoor plumbing, families are able to enjoy the comfort and convenience along with clean drinking and bathing water. But, many homeowners do not understand their home drain lines or how they work, even though they use them multiple times every day.

Drainage systems are different than water systems in that they do not rely on pressure to move supply through the pipes. Residential drainage systems use pitch and angles to move waste and wastewater from the drain lines into the main sewer line and eventually into the city’s waste sewer lines. From there, it goes to treatment facilities or septic tanks.

The sewer line is the 4-inch line that all other residential drain lines empty into. The drains inside the home are typically 2-inch lines. There are also vent lines, which keep drain smells from lingering in the home, traps, and cleanouts. All drain line components help keep the home free of sewer gases, enable effective methods of snaking and cleaning out the line, and trapping odors and debris in the line.

Often kitchen drain lines are connected to laundry drain lines and bathroom drains and toilets can be back to back or side by side, but every home can vary. It is important to always hire a professional drain technician, since not every home will be the same. Understanding how the drains work is crucial to properly cleaning, repairing, and diagnosing drain pipe problems.

What is a Sewer Line?

Whether the home is multiple story or single story, all 2-inch drains eventually drop into the main sewer line through tie-ins on each individual line. The main sewer line can be installed under the slab foundation and run underneath the yard or underneath the house for homes on raised foundations.

Typically, main sewer lines will have at least two cleanouts, an end of the line and front cleanout. Critical to clearing mainline clogs and avoiding sewer backups is to have proper cleanouts. Homeowners with buried cleanouts often have to spend more to have professional plumbers snake from the roof vent line or pull the toilet and snake from the flange. Installing cleanouts is good for homes that constantly experience sewer line problems due to frequent backups. It’s important to schedule preventative maintenance for easy access.

Many homeowners do not know that the city of San Diego is not responsible for any portion of the main sewer line from the edge of the city sidewalk. Professional plumbers recommend every homeowner run a sewer camera inspection at some point to understand where their cleanouts are and where their line connects to the city to have for reference when problems arise. It could save time and cut costs.

When Does a Sewer Line Need to be Replaced?

A sewer line can be made out of different materials and will depend on when and where the home was built. Older homes that have been around for more than 30 or 40 years will have a cast iron or clay sewer line underground, cast iron or ABS plastic if it is under a raised foundation. Many newer homes are being built with ABS plastic.

Cast iron has a lifespan of between 50 and 80 years. This does not guarantee issues will only arise after its lifespan, but it is long lasting when properly maintained. Outside elements, however, will affect cast iron and clay, especially, and cannot be stopped by any means of maintenance.

Root intrusion is a likely culprit in many failing sewer lines underground. As cast iron ages, it can deteriorate. Shifting in the earth can also offset all types of drain lines. Clay sewer lines are all installed in five-foot sections, so there are hubs holding them together. When those hubs fail, or a break occurs in any line, tree roots can seep into the line and overtake it easily. Roots gravitate towards the nutrient-rich elements and moisture in the main sewer line. It is the perfect environment for roots to grow.

When roots do break into the line, sometimes hydro jetting can clear them and restore the pipe to normal conditions. A plumbing contractor will first perform a pipeline camera inspection to view the line, inspect the level of root intrusion or cause of the blockage, and verify there are not any cracks or breaks in the line.

Main sewer lines often need to be replaced when there are large breaks or holes, or whole sections are missing. This can be caused by excessive roots, age, deterioration or ground shifting (for main sewer lines in the ground).

Main sewer lines under the house are not exempt from problems or breaks that may require drain pipe replacement. Often, when sewer lines that are exposed in a crawl space exhibit problems, homeowners will smell sewer gases from leaks or breaks, notice sewage spills under the home, or experience other drain issues.

How is the Sewer Line Replaced?

In order to determine if the sewer line underground needs to be replaced, first a camera inspection is performed. The pipeline camera inspection will locate the depth of the line, the length of the line in need of replacement and other conditions to determine the scope of work.

Replacing a main sewer line underground requires digging into the ground, often disrupting landscaping and concrete. If the line is broken under a city street, it will increase the repair costs and job requirements, as city permits and safety control will be necessary. But don’t worry, there is an alternative and we will discuss that next.

Sometimes, a sewer line is only in need of a small repair and the plumber will dig down to the pipe, cut the affected area, replace the broken section and backfill with the native soil. It can be as simple as that, or require a backhoe or excavating crew and finish work. It all depends on how much of the line needs to be replaced.

Replacing a main sewer line underneath a raised foundation, as opposed to a trenchless area, is often much easier, as long as there’s crawl space access. Plumbers are used to crawling in all kinds of spaces and can make many repairs right from under the house. If there is no crawl space, or no access, a plumber may have to go through the home floor to get to the broken sewer pipe. A camera inspection can be performed if a visual assessment is not available.

At the end of the day, the main sewer line replacement cost will vary greatly and it is important to hire a licensed contractor so you know your home and property will be protected at all times. A camera inspection is also a must to get an accurate cost estimate for underground lines or inaccessible lines under the home, where it may be necessary to utilize alternative trenchless technology. Be wary of ballpark figures without a thorough inspection.

Is There an Alternative to Sewer Line Replacement?

Great news for homeowners who have lots of concrete, expensive landscaping, or if their sewer line runs underneath a city sidewalk or street– there is an alternative to replacing the entire line or even a section of the line.

Epoxy relining solutions is a great way to repair a failing sewer line, stop root intrusion for good, or make small repairs in places a plumber is unable to dig.

Epoxy pipe relining is a process that inserts an epoxy resin solution into a sewer line where it is inflated to mold to the interior of the pipe, and is then left to cure. Once cured, it hardens into a virtually indestructible plastic pipe, restoring flow and saving a lot of time and money.

But, the first step to sewer line replacement is a camera inspection and proper diagnosis form a drain expert. So call Bill Howe, San Diego drain experts for over 35 years. Our technicians offer both epoxy relining solutions and traditional dig ups and sewer line replacements.

For an estimate to diagnose and solve your sewer line problems for good, call 1 (800) BILL HOWE (245-5469), visit us on live chat, or book a service online today.


Leave a Reply


  1. […] A sewer line camera inspection will provide not only an in-depth view of the line’s condition, but it also helps to trace the line. It can show how far below ground the pipe is installed, where it runs underneath landscaping, concrete, and the home, and if potential issues are in the line that may cause future blockages. The service will help diagnose whether it is necessary to replace the underground sewer line. […]

  2. Edward Y Mei

    Does the City of San Francisco allow for the use of epoxy pipe relining for single family home residences. If not, why not?

  3. Deborah

    We had our cast iron pipes replaced and the concrete patched but now we’re seeing some hairline cracks around the edges. The plumbers said that they did not use rebar. Is that standard practice? Without rebar, how does the new concrete “join” with the old concrete?

  4. Christine Dejesus

    Replacement of a clay sewer line

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