Under-slab drain line leaks
Under-Slab Drain Line Leak Repair Services in Texas
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Most slab leaks are in the pressurized supply lines. The drain lines that carry waste water out of the house also run under the concrete, and they can crack, shift or separate. Call and we’ll connect you with a local Texas crew for under-slab drain line leak repair.
Tell us what you’ve noticed and we’ll connect you with a local crew.
How a drain line leak differs from a supply leak
A supply line is under pressure, so a leak pushes water out continuously and shows on the meter. A drain line is not under pressure. It carries water and waste away by gravity, and it only leaks while water is moving through it, mostly when a fixture is used.
That changes how it shows up. There may be no meter movement and no warm spot. Instead, the signs appear after a shower, a load of laundry or a run of the dishwasher.
Signs of a drain line leak under the slab
- A persistent sewer smell in a room or near a floor, especially after using water.
- Damp or stained flooring in a place that is not near a supply line or a fixture.
- Gurgling or slow drainage in several fixtures at once.
- Soil settling or a soft area near the slab’s edge outdoors.
- Unexplained pests entering around the floor or baseboards.
Several of these have other causes, so a technician confirms the source before recommending any repair. If you smell gas, leave the building and call the gas utility and emergency services from outside. That is a different problem from a drain smell.
Describe the smell, the damp spot or the sound.
Why drain lines under slabs fail
- Movement. Soil and slab shift and can pull joints apart or crack a pipe.
- Age and material. Older cast iron corrodes from the inside. Some plastic drain lines were installed with joints that loosen over time.
- Root intrusion. Roots can enter a joint and widen it.
- Poor slope or bedding. A line that was not bedded well can settle and sag.
- Construction damage. A pipe can be cracked when the slab was poured or by later work.
How a technician confirms a drain line leak
- History and symptoms. The technician asks when the signs appear and which fixtures are involved.
- Camera inspection. A small camera is run through the line to look for cracks, offsets and separations.
- Locating. A locator traces the line’s path and depth so the problem spot can be marked on the floor.
- Testing. The line may be filled and checked for loss, or water may be run while the area is observed.
This page is about finding and repairing leaks. Clearing blockages and drain cleaning are different jobs and are not offered here.
A technician can confirm whether the drain line is leaking.
Repair options for a leaking drain line
Spot repair through the slab
The slab is opened over the damaged section, the pipe is repaired or replaced and the opening is patched. See spot repair.
Rerouting the drain
Because drains rely on slope, a reroute needs planning. In some homes the drain can be moved to run above the slab, which is more involved than moving a supply line, so a technician has to confirm it is practical.
Replacing a longer run
If the camera shows damage along a longer stretch, replacing the run may make more sense than several repairs.
Spot repair or rerouting, explained for your line.
Drain lines in Texas slab homes
Clay movement in North Texas, wet soil in the Houston area and the age of many cast iron systems in older homes all play a part. In Dallas-Fort Worth homes built from the 1960s through the 1980s, drain lines of cast iron or early plastic are common under the slab.
Where a leak is found in a drain line, ask the technician whether the supply lines in the same area were also checked.
Describe the signs you have seen.
Cast iron and PVC drains
Most slab homes in Texas have one of two drain materials under the slab. Older homes, roughly those built before the 1970s and into that decade, often have cast iron. Newer homes usually have PVC or ABS plastic.
Cast iron fails mainly from corrosion. Over decades the inside of the pipe can scale and rust, and the bottom of the pipe can wear thin where water runs. Cracks and holes may follow, and joints can separate as the soil moves.
Plastic drains do not corrode in the same way, but they can crack, separate at joints, or sag where the soil beneath them has settled. A belly in the line holds water and debris and can lead to backups. Both materials can be affected by roots where a line runs near trees.
Many homes have a mix, with original cast iron in some sections and plastic where repairs were made.
What a camera inspection shows
A camera inspection is the main way to see inside a drain line. A small camera on a flexible cable is fed into the drain through a cleanout or fixture opening, and the technician watches the picture on a screen.
The camera can show cracks, holes, separated joints, roots, sags and buildup. Many systems also have a locator that lets the technician mark the camera's position on the floor above, which shows where a problem is under the slab.
Ask to see the footage, or ask for a copy. It helps you understand what was found, and it is useful if you want a second view on the repair. A camera inspection does not always find a leak on its own, so it may be paired with other tests. See how slab leaks are found.
Roots and drain lines
Tree roots look for moisture, and a small crack or loose joint in a drain line can draw them in. Once inside, roots grow and can widen the opening, trap debris and cause slow drains or backups.
Homes with large trees close to the house are more likely to see root problems, especially with older cast iron or clay sections near the exterior. A camera inspection shows whether roots are present and where. Clearing roots can restore flow for a time, but the opening that let them in usually needs to be repaired for a lasting fix.
If you are planting near the house, ask a nursery about root spread and keep large trees well away from the foundation and the main drain route. A plumber can show you roughly where the drain line leaves the house, which helps when planning new beds or trees.
Regular camera checks every few years can catch root problems early in homes with older drains and large trees nearby.
Under-slab drain line questions
Yes. Cracks, offset joints and corroded pipe can all let water out, usually when a fixture is in use.
Not usually. Drain lines carry water out of the house, so a leak does not show on the meter.
A sewer smell is the most common sign, often strongest after using water.
A camera inspection, locating the line and testing for loss are the usual steps.
Sometimes. Drains rely on slope, so a technician has to check that it is practical in your house.
No. A clog blocks the flow. A leak lets water out of the pipe. A line can have both.
Leaking water can soften soil under a slab. If you are worried about the structure, ask a foundation contractor, since structural repair is a different trade.
A restoration company dries and cleans affected areas. The plumbing crew repairs the line.
It is worth asking. A technician can confirm whether nearby supply lines are sound while they are working.
Get the drain line checked
Call and we’ll connect you with a local technician who can confirm the leak and explain the repair.
A local crew knows how homes in your area are usually plumbed.