Trenchless Sewer Repair and Cleaning 101

By Denise Sullivan
Published: December 15, 2020 | Last updated: July 5, 2023
Key Takeaways

Avoid costly sewer repair. Corrosion, leaks and tuberculation in sewage pipelines can be mitigated by proper maintenance and trenchless rehabilitation.

Underground and unnoticed, sewer pipes are often neglected. It is not until something goes wrong and sewage is backed up onto someone's lawn, into their basement or in the middle of the city, that many homeowners and officials even give these lines a second thought. A regiment of cleaning and repair, when necessary, can keep the pipes flowing and avoid a nasty ordeal.


Why Clean and Repair Sewer Lines?

When a sewer line becomes clogged, waste begins to back out of the plumbing. This waste comes with a horrendous smell and creates unsanitary conditions as it backs up onto your lawn, in your sinks, tubs, and in some cases, may even flood your basement. By periodically cleaning out the lines, you can avoid these circumstances.

Repairs to sewer lines are equally important. Cracks in the line can cause waste to seep out into the surrounding soil. This leakage can cause contamination of the water table. Through early leak detection, prompt repair negates the need for full line replacement.


Having a clogged pipeline is a problem for all homeowners. Issues such as tuberculation, grease, and tree roots are not the only problems that owners face.

What are the best ways to fix the lines using trenchless methods to keep the owners from digging up their yards for repair?

Issues that Clog or Break Lines

There are different issues that homeowners face when it comes to pipeline issues. Each issue is caused by a slightly different problem and can and should be addressed early to prevent further damage.


Tuberculation develops in cast iron pipes over time. It is the build-up of slime caused by iron eating bacteria. The bacteria begin metabolizing ions from the water in the line and start dissolving the pipes.

As the pipes begin to dissolve, the interior becomes rough and jagged—debris flowing through the line snags on the interior, causing the line to clog. The tubercules can build up and begin to narrow the pipe's interior, causing it to restrict water and sewage flow and build up pressure in the line. (Read also: Cleaning and Repairing Tuberculation in Pipes.)



Grease is a sewer line problem caused by carelessness in households. It begins when someone is cooking meat, and the fat begins to turn into oil in the pan; bacon is a prime example. Then the cook pours this hot liquid down the kitchen sink. While the heat may not damage the pipeline, another problem will eventually cause a clog, when it gets big enough, they call it a "fatberg."

Grease rendered from meats or heated lard solidify when they cool. A small amount of oil will not immediately clog the pipe. However, the kitchen sink's constant use as disposal for grease will cause a build-up that will block the line and force the owner to call a plumber. A 40 tonne fatberg was discovered under London UK in 2019, wreaking havoc on the sewer system. The results can be massive and massively expensive.

Tree Root Infiltration

Sewer lines made from a porous material, such as clay, are susceptible to root infiltration. As trees grow, their roots go deep and wide in search of water to help them live and grow.

Sometimes they find older, porous lines that make it easy for their roots to latch onto and infiltrate to get to the water inside. Pushing their way into the pipe causes cracks and will eventually cause the line to break.

Sagging Lines

Sagging lines is something that happens over time. It is caused by soil conditions changing to the point that the line begins to lose its support. When this happens, a belly forms at the low spot. The belly becomes a collection point for waste to build up and clog the line. Unlike other blockages and clogs, this problem is something that the homeowner cannot control and probably won't know has happened until it's too late.

Internal Corrosion

Corrosion occurs in metal pipes due to a reaction between the metal and its surroundings. This electrochemical reaction causes the metal to rust (oxidize). As the pipeline begins to deteriorate, it loses integrity. Eventually, it will cause the line to crack or break, causing a leak from the pipeline

While all metal pipelines can succumb to corrosion, lines that carry agents such as carbon dioxide, hydrogen sulfide, and water are more prone to corrosion than other pipes. (Read also: Corrosion Mechanisms of Buried Pipes.)

Correcting Issues – Cleaning

Cleaning pipelines is the first step to ensuring they remain in working order. Different solutions are depending on the issue.


Before the cast iron line can be protected from future tuberculation, workers must first remove the build-up. To do this, they need to use an abrasive jetting machine (AJM), to remove the sludge with an abrasive, low-pressure spray. Depending on the solution used, the spray may contain solution and water or just solution.

Once workers remove the build-up, they can focus on preventing the build-up from recurring. Workers will place an interior liner to keep bacteria from feeding on the inside of the cast iron line. There are a couple of different options to line a cast iron pipe. However, the most used process is the cement-mortar lining.

To install mortar into the line, workers place a nozzle into the pipe and apply the mortar throughout the pipeline. Once the mortar cures, the pipeline can be put back into service without the worry of tuberculation reoccurring.


Regular line maintenance goes a long way to preventing grease build-up. Using vinegar and baking soda regularly can help keep oil and grease from building up within the line. Not pouring grease down the sink is the best way to keep it from becoming a problem. Instead of using the sink as a catchall, use a metal can, such as an old coffee tin or soda can, or a jar to collect the grease. Once it cools, dispose of the container.

If grease still gets into the line and eventually builds up to clog it, the use of hydro-jet cleaning will clear the clog from the line. Hydro-jet is, as the name implies, it is a high-pressured hose that produces a stream into the clogged pipe and removes it. Grease build-up moves down the line into a more open sewer, clearing the homeowner's line. This method can also break tree roots and clear them from the line before repairing it.

Correcting Issues – Repair

While cleaning does help restore the use of some pipes, some are so severely damaged that they need repair or replacement before the pipeline can be put back into service.

Tree Root Infiltration

The first step in repair a line with root invasion is to clear the line of the infiltration before beginning. Thicker lines such as cast iron or clay can withstand workers cutting the interior's roots to remove them. However, a pipe made from corrugated iron is too thin to use a cutting tool. The tool could inadvertently pierce the line and cause more damage than the root. In this case, a high-powered water stream may be needed to break the roots. This method should be used with caution as it may also damage the pipe. Instead, chemicals are necessary.

Once the line is clear of roots, it is time to repair it. It is a good idea that all lines, no matter how infiltrated they were, be treated with a de-rooting chemical. The chemical will slow re-infiltration. If the lines are not too damaged, repairing loose joints and filling in holes and cracks can prevent future problems.

If it more than light cracks, then the pipe may need to be lined to prevent future issues. Using a cured-in-place pipe (CIPP) is the simplest option. Workers run an epoxy resin permeated fabric into the damaged line. Once in place, workers inflate it using a bladder and then allow the resin to cure. The liner uses the old pipe as a support structure while it becomes the new water and waste flow line.

Sagging Lines

For a sagging line, there is no cleaning before repair. While most companies will suggest an open trench to repair a belly, there is an alternative to having the yard dug up for days on end. Instead, they use of pipe bursting can have the old line replaced within a day or two. (Read also: Sliplining or Pipe Bursting for Pipe Repair?)

To burst the pipe, workers dig small entry and exit trenches. They then use a bursting tool that runs through the line destroying the pipe already in place. Behind the bursting tool is the new pipeline, which the tool pulls into place as it makes its way through the line. Workers then connect the new line to the existing lines and fill in the holes.

Internal Corrosion

To begin repairing a pipe with internal corrosion, workers must clean and descale the line. Hydro jetting is one way of clearing the pipelines. However, lines with excessive build-up may not respond well to jetting. The use of a descaling tool may be a better option. The descaling machine has devices that attach to the rotating cable. The motion allows the tools to scrape the inside of the pipe and remove build-up.

Once the line is free of corrosion build-up, workers need to assess the amount of damage. Lines with rust but not many cracks can benefit from using the CIPP method of repairing the pipeline. Other lines that have suffered significant damage, including channeling, may need to be replaced. To replace the old pipe with a new one, pipe bursting is the better choice.


Issues that may clog or break a line are not always apparent to the owner. Sometimes they don't know there is a need to clean or repair the sewer line before it arises. Just because a line is blocked or cracked does not mean damaging the yard to do so. A licensed technician can track the problem down and make the appropriate recommendation.

Share This Article

  • Facebook
  • LinkedIn
  • Twitter

Written by Denise Sullivan | Technical Writer @ Trenchlesspedia

Denise Sullivan

Denise Sullivan is an accomplished freelance writer from Louisiana, with a Associate's Degree in Journalism from Eastern Oklahoma State College. She also graduated from East Central University with a Bachelor's in Biology. Denise began her writing career writing operations and maintenance manuals and software utility manuals for flight simulators. Since, she has expanded her writing to a broad spectrum of topics.

Related Articles

Go back to top