This Is How To Find Sewer Line Under Concrete Slab

This Is How To Find Sewer Line Under Concrete Slab

If your house is connected to the sewage system, a sewer line connects your drains to the main sewer drain. Sewer lines run underground and take wastewater from your home to the city’s main septic tank. 

When renovating a home or setting up a new sink or toilet, any homeowner would want to be so sure, they don’t damage the sewer line in the process. If this happens, finding the sewer line can be quite a chore.  

But in this article, you’ll find information on the causes of sewer line blockage, how to unclog a blocked sewer line, and the best sewer line pipe to use.  

How To Find Sewer Line Under Concrete Slab

But firstly, follow the steps below to find a sewer line under your concrete slab.

Step 1: Buy or rent a pipe detector from a local retailer. Make sure the transmitter and the detecting device are on the same frequency.

Step 2: Insert the detector line into a sewer cleanout or drain for about 15 feet. If possible, avoid using a toilet because the device doesn’t perform well while submerged.

Step 3: Point the device vertically toward the ground. 

Step 4: Rotate the device till you hear a loud beep signal. The device should be most audible at the end of the line. There may also be arrows on display to indicate when you are going in the same direction. 

Step 5: Use a pipe locator to mark the position of the pipe with a flag once you’ve found the sewer line. 

Step 6: Return to the detector line’s original location and unwind a little more into the pipe. Then you’ll need to use the detector to find the line once more. Erect a second flag after you’ve found the sewer line the second time

Step 7: Repeat this operation many numerous times, and erect flags wherever you discover the underground sewer line. The flags will help you to track where the sewage line is as you proceed. 

In addition, you also have the option of contacting a professional plumber for assistance in finding sewer pipes beneath the ground. 

The plumbers will come to your house and identify the pipes that connect to your sewer line, as well as use tapes to map out the sewer line areas.

Furthermore, you can call your city office to tell you where your home’s sewer line is located. They can show you where the line connects your house to the city’s mainline. Also, they’ll inform you of how long the pipe is, how deep it is, and if it is public or private.

What Private Sewer Line Is

A private sewer line is a pipe that connects your home’s sewage to the public sewer line. This line transfers all wastewater from your home to the sewer, including everything flushed down the toilet and cleaned down the sink. 

These private sewer lines are necessary for diverting wastewater from homes, schools, churches, and companies to a public sewage collection and treatment system.Private sewer lines are sometimes known as side sewers. 

These side sewers are made up of two parts. 

The upper sewer line: This section of pipe runs closer to the house, from the building drain to the sidewalk.

The lower sewer line: This section of pipe runs closer to the street, including the space between the sidewalk’s drain and the public sewage main. 

What Causes Sewer Line Blockages?

Flooding, slow water drainage, corrosion, and costly repairs adversely affect a blocked sewer line. Check out the common causes of clogged sewer lines below. 

Sagged sewer lines:

Sagging sewer lines happens gradually, out of a homeowner’s control. When a portion of pipe sinks owing to ground or soil conditions, it is called a “bellied” pipe.

The low point in the sewer line will accumulate paper and garbage, causing repeated sewer line clogs.

Damaged pipes:

When sewer pipes break or rupture, sewage cannot flow freely through the system, resulting in rapid and frequent backups. 

An earthquake can cause sewer pipe damage, heavy construction equipment above ground, shifting soil, or increased traffic.

Sewer lines that are cracked, collapsed, or broken can cause floods and backups in your house or garden, similar to clogged sewer lines.

Food waste:

Never flush excess food down the drain. You can set up a compost pile to trash the food wastes. The compost pile is essential for non-biodegradable waste such as ground coffee, tea leaves, and oil.

Avoid flushing grease or oil down the drain because they would solidify in the pipes and block them. Instead, soak up the oil with a paper towel and trash in the compost pile.

Tree roots:

During dry seasons, large trees and plants in your yard will naturally seek water sources beneath the soil to survive. Your sewer line is generally the closest water source, especially if it’s close to a tree or bush. 

Although it takes time, roots can eventually reach the sewer system at its joints, causing blockage or severe damage.This problem is prevalent in old houses with outdated plumbing.

Mineral buildup:

Minerals dissolved in hard water can accumulate and form insoluble lumps, which can easily clog drains.  If hard water is common in your neighborhood, one alternative is to install a water softener in your home. 

You may also need to descale and remove debris and buildup regularly. Unfortunately, mineral buildup clogs can be tough to remove after they’ve formed. Therefore, if your sewer lines are clogged by mineral buildup, you may have to call a professional plumber.

How To Unclog Your Sewer Line? 

A main sewer line blockage does not occur immediately. However, the nasty consequence of a clogged sewer line is that your kitchen and toilet wastes remain in the tub rather than draining off. Follow the steps below to unblock your sewer line. 

Step 1: Remove the lid of the drain pipe

Unscrew the lid with a pipe wrench.

Step 2: Remove the cap to drain off the buildup

Step out of the way and the cap quickly. Any trash that has accumulated due to the clog will stream out of the mainline drain. Allow it to drain off before making any repairs.

Step 3: Insert the drill cable into the drain pipe

Ensure to read the manual for directions to get the maximum result because each drill is unique. However, the general rule is to slowly insert the drill cable into the drainpipe until you hit the blockage.

Step 4: Run the drill until the blockage is clear

Allow the drill to continue running until the blockage is gone. When this happens, you’ll be able to see it because the water level in the drainpipe will gradually fall before draining completely.

However, don’t turn off the machine as soon as the clog is gone. There could still be smaller debris somewhere in the pipe, posing more concerns in the future.

Step 5: Rinse the pipe and the drill with water

Spray the hose down your drain line at full pressure once the clog has been dislodged.  The water will clear any leftover debris in the pipe and the drill.

Step 6: Carefully remove the drill from the pipe

Pull the plumbing cable out of the pipe one at a time, hosing off any debris as you go. Rinse the drill cable a few times before looping the drill cable back onto the machine. When you’re through, replace the cap on your drainpipe and tighten it using the pipe wrench.

Types Of Sewer Line Pipes

Your pipes depend on the age of your home, including whether the sewer line has ever been renovated or fixed.  The most common pipe materials are clay, cast iron, and PVC.

Cast iron:

Cast iron is still used in many homes because it is about as strong as it gets. Unfortunately, the iron is quite heavy, requires specific tools to cut, and is too expensive. 


Clay is still good material for sewer pipes in the twenty-first century, despite its archaic appearance. Clay is the most natural of the three materials. 

A clay system’s structural integrity gives it its durability. So, clay will not flatten or bend under a big load of water-soaked soil.

Clay has a setback of being too heavy and difficult to cut. In addition, while the clay is chemically resistant, it’s highly porous, attracting roots to grow into the pipe.


PVC is the best option among drainage specialists, builders, and homeowners because of its low cost and easy usage. PVC is very light and flexible, making it simple to install. In addition, it’s firm, making it highly durable.

The root-resistant and smooth interior of the pipes allow waste to flow freely to the sewer or septic tank. Overall, PVC has the lowest risk of damage and repair, and it’s the simplest to repair even when it damages.


One of the most expensive and irritating home plumbing issues is repairing or replacing a sewer line.The sewer line carries all of your wastewater from your home to the sewer main below the pavement. 

Whether for repair or replacement purposes, you should be able to find your sewer lines under the concrete slab without damaging the concrete slab or hitting your water appliances.

Do you plan to renovate your home anytime soon? Would you love to install a new bathtub or toilet sink? Then, get your simple tools, follow the steps above, and quickly locate your sewer line.

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