Tunneling means we dig underneath your foundation from outside and repair the broken drain line from below, instead of jackhammering a trench through your floor. For a house it saves your flooring; for a care home, restaurant or office it is the difference between staying open and shutting down.
MVP Plumbing tunnels under slabs across Baytown, Mont Belvieu and the Houston area. Licensed master plumber, MPL 38224. Call 832-334-2836.
Do I have a broken line under my slab?
Most people arrive here through a drain that will not stay fixed. These are the signs that point under the slab rather than at a blockage:
The one most people miss: a drain that clears but still smells, gnats in the kitchen that will not go away no matter how much you clean, and water surfacing outside around the building. Those three together usually mean a broken line under the slab, not a blockage.
- The line sits full of water after it has been cleared. That means it has lost its fall.
- The same stoppage on a schedule — every few weeks or months, in the same place.
- A smell, and gnats, that cleaning does not fix.
- Water surfacing in the yard or around the building.
- More than one fixture affected at once, which points at the main line.
- Cracked or shifting flooring along the line's run in a slab house.
Most people do not connect a fly problem to a plumbing problem. It is worth saying plainly: if you are cleaning constantly and the gnats keep coming back, the problem may be under your floor.
What does the diagnosis actually involve?
We do not dig on a hunch. The path is always the same:
- Clear the line first. A blockage and a broken pipe look identical from the fixture.
- Watch how the machine behaves. A cable catching repeatedly at the same distance, or a line that clears and refills, is the signal.
- Camera the line. This answers the only question that matters — blockage or pipe — and tells us exactly how far along the problem sits.
- Scope and quote before anything is dug.
That camera distance is what makes a tunnel a targeted dig rather than an exploratory one. See drain cleaning for the first half of that path.
A fifteen-foot tunnel in Clear Lake
Job notes · Clear Lake, residential
The customer called about a sink that was not draining properly. We ran the drain machine and could tell something was not right, so we put a camera down the line.
The camera showed the line sitting full of water, which meant at minimum it had lost its fall. The customer chose to have it repaired properly rather than patched. We tunneled fifteen feet under the slab and found the line had shifted underground and pulled apart at a joint. We replaced the damaged sections and anchored the new pipe to the underside of the slab with hangers so it cannot sag again.
Timeline: one day to dig the tunnel. Three to four hours the next day to make the repair. Then we tested everything, had the customer run water through it, and ran the camera again before allowing the backfill on day three.
Note the last step. The line was cameraed again before the backfill went in, while the work was still visible. What you are paying for gets verified while anyone can still see it.
Why do you anchor the new pipe?
The pipe does not shift unless the slab does.
The obvious question after a tunnel job is what stops it happening again.
New pipe is anchored into the concrete slab with hangers, not left resting on dirt. When the tunnel is backfilled the pipe cannot move, so the backfill cannot create a new belly.
This is worth asking any plumber about before they start, because it is the part of the job you cannot see once the work is finished. Backfill settles. A new line laid on settling dirt develops the same belly the old one had, and by then it is somebody else's warranty.
Why tunnel instead of trenching through the floor?
Tunneling means the work happens underneath the slab instead of through it.
For a business that cannot close — a care home, a restaurant, an office — that is the difference between staying open and shutting down. For a house it means nobody breaks out your flooring, jackhammers a trench through your living space, repours concrete, and leaves you to sort out the floor covering afterwards.
On the invoice line it is not always the cheaper method. Once you count flooring, dust, disruption and days out of the room, it usually is.
Can you work while the building stays open?
Job notes · Baytown — assisted living facility (in progress)
A facility we have looked after for the last three or four years. Their kitchen drains had been backing up. We cleared them, but the customer still had a smell and was getting gnats in the kitchen no matter how much they cleaned. They were also noticing more and more water surfacing outside around the building. Best estimate is the line has been leaking since around 2020.
Scope: ninety-five to one hundred feet of tunneling, up to fifteen drains being replaced. All of it underground, with the building open and residents in it throughout.
That building cannot close, cannot relocate residents, and cannot have its kitchen out of use. Tunneling is what makes the job possible at all. See commercial plumbing.
It is also a fair illustration of how long these problems run before anyone identifies them. Best estimate is that line had been leaking since around 2020 — through repeated drain clearings that each worked for a while.
What does it cost, and can it be financed?
We do not publish prices for this work, because the number depends on the length of the tunnel, the depth, the soil, how many drains are being replaced and what the camera finds. Anyone quoting under-slab work from a website has not seen your line.
What we will do is look at it, camera it, and give you a real number before anything is dug.
Financing is available through Acorn Finance and appears as an option on the estimate we send you — so the first step is asking for a quote. This is one of the jobs financing genuinely helps with, because it arrives unplanned and it gets worse and more expensive the longer it waits. See financing.
Related work
Drain cleaning is where most of these jobs start · camera inspection is what turns a guess into a scope · sewer line repair and replacement covers yard lines and partial replacements · hydro jetting often comes first so the line can be seen.
Tunneling across the Houston area
We tunnel in Baytown, Mont Belvieu, Clear Lake, Beach City and across the wider Houston area. See service areas.
Common questions
What is tunneling under a slab?
Tunneling means digging a passage underneath your foundation from outside, so a broken drain line can be reached and replaced without breaking through the floor inside the house. The alternative is jackhammering a trench through your slab, through whatever flooring is on top of it, and repouring afterwards.
How long does a tunnel job take?
On a fifteen-foot residential tunnel in Clear Lake it was one day to dig the tunnel, three to four hours the next day to make the repair, then testing, running water through it, and cameraing the line again before we allowed the backfill on day three. Larger commercial jobs run considerably longer - one care home job is ninety-five to one hundred feet.
Do I have to move out while you tunnel?
No, and that is most of the reason to tunnel. The work happens underneath the slab and the access is from outside, so nobody is cutting your floor or running a jackhammer inside the house. At an assisted living facility in Baytown we are doing this with the building open and residents in it throughout.
What stops the pipe from breaking again?
New pipe is anchored into the concrete slab with hangers, not left resting on dirt. When the tunnel is backfilled the pipe cannot move, so the backfill cannot create a new belly. The pipe does not shift unless the slab does.
Why does my drain keep backing up after it has been cleared?
Because clearing a line does not fix a line that has moved. If the pipe has lost its fall - the slope that makes a drain work - water and waste sit in it no matter how many times it is cabled. A camera is what tells the difference between a blockage and a pipe problem.
I have gnats and a smell in the kitchen but the drains run. Is that plumbing?
It can be, and most people do not make that connection. A drain that clears but still smells, gnats in the kitchen that will not go away no matter how much you clean, and water surfacing outside the building - those three together usually mean a broken line under the slab, not a blockage.
Is tunneling more expensive than breaking the floor?
On the line item, usually yes. Once you count replacing the flooring, the dust, the days out of the room and the concrete work, it is often the cheaper of the two. Financing is available and this is one of the jobs it was made for.
How do you know where to dig?
The camera. It tells us how far along the line the problem is, which is what turns a guess into a targeted dig. Digging without that is how people end up paying for exploratory holes.
Last updated · written by a licensed master plumber, MPL 38224