You’ve already made the smart choice to avoid breaking through your floors and slab by choosing under-slab tunneling for your plumbing issue. It’s cleaner, more convenient, and keeps your home life much less disrupted. But now you’re wondering, “Okay . . . so how long is this going to take?”
Time matters, especially when plumbing problems are involved. As much as we like to be absolutely precise in estimating job duration, sometimes it just doesn’t happen exactly like we hope it will go. That said, we’ve tunneled thousands of feet in the last 40+ years and have a pretty good idea of what to expect if Anchor Foundation Repair is on the task.
Let’s walk through how long our tunneling projects typically take, what can affect the timeline, how plumbing fits into the process, and what it takes to get that tunnel filled back in.
How Long Does It Take to Tunnel Under My Slab?
Tunneling under your home to reach broken drain lines isn’t an overnight job, but it’s usually not an extremely long one either. The total time depends mostly on how many feet of tunnel are needed.
Here’s a quick breakdown of typical dig durations based on tunnel length:
- 1 to 8 feet: Usually takes 1 day
- 9 to 16 feet: Expect about 2 days
- 17 to 25 feet: Around 3 days
- 26 to 34 feet: Plan for 4 or more days
A tunneling crew works during this time to create a 3 x 3 foot square tunnel that follows along your drain line to the source of the problem. These tunnels take time because they have to dig under the perimeter beam, back up the other side of the beam to reach the underside of the slab, which serves as the ceiling of the tunnel. This is for safety to prevent cave-ins.
This part of the tunneling process is strictly about digging the tunnel and dirt removal to gain access to the problem plumbing. It doesn’t include how long the plumbing work or the backfill process will take – that’s coming up.
What Else Affects Tunneling Time?
Not every tunneling job is the same. Some factors can speed up the job, while others can slow it down a bit. We wish we could control all of these, but some just come with the territory. Here are the most common reasons why tunneling timelines might stretch a little:
- Where you live: Homes that are farther away from our base (like out in the country) cut into daily dig time due to longer travel times.
- Beam depth: Deeper perimeter beams (especially common in newer homes) make digging the initial access hole more difficult and time-consuming.
- Tunnel starting point: If the tunnel has to start in a hard-to-reach spot, like under a patio, behind a deck, or deep in the backyard, it adds challenges to the dig.
- Soil conditions: Soft, loose soil is quick to dig through. But hard-packed clay or rocky terrain slows us down and requires more cautious excavation.
We plan ahead for these challenges and always dig with safety and structure in mind, which sometimes means the job takes a bit longer. You can be assured that your tunneling job with Anchor will be done right.
What About Timelines for Under-Slab Plumbing Repairs?
After the tunnel is dug, it’s time for the plumber to step in. While we don’t do the plumbing repairs ourselves, we do help coordinate with your plumber to keep things moving. But unlike the tunnel dig, the plumbing timeline is much harder to predict.
It’s important for your under-slab plumbing repairs to be done appropriately for the under-ground environment. You don’t want to rush this part of the deal.
Several factors can influence how long the plumbing portion takes:
- Plumber availability and responsiveness: Some plumbers are ready to go right away, while others may take a few days to show up.
- Number and severity of breaks: A single break is faster to fix than multiple areas of damage or extensive pipe deterioration. Plus, sometimes more issues are discovered once the lines are reached and inspected.
- Type of pipe: Repairs on old cast iron pipes are typically trickier and more time-consuming than on newer PVC lines. It can take extra time and work to find intact pipe to tie into.
- Weather: Rain can delay both tunnel work and plumbing access, especially if things get muddy or unsafe.
If you already have a plumber lined up and ready, great! If not, we’re happy to coordinate with one on your behalf (we do have some plumbers that we trust and recommend). Just know that this part of the process can vary the most in timeline.
Your chosen plumber will have a way better repair time estimate than we could venture to guess. For a more accurate timeline, you should ask them for their best estimate for their part of the process.
How Long Does It Take to Fill the Tunnel Back In?
Once the plumbing is repaired and inspected, it’s time to close things up. Backfilling is where we put all the dirt back in the tunnel and make sure everything is safe and solid under your home again.
The backfill process takes about this long, again depending on the length of the tunnel:
- 1 to 16 feet: Typically 1 day
- 16 to 26 feet: Usually 2 days
- 27 to 34 feet: About 3 days
- 35 feet or more: Expect 4 days or more
We don’t rush the backfill process. It’s important that it’s done correctly to support your foundation and avoid creating future problems. Not only do we put dirt back in, but we also pump in something called slurry to fully support the previous tunnel space and your home.
If you want to know the best practices for backfilling tunnels, we’ve got a great article on that. It’s linked for you below.
How Your Tunnel is Backfilled is Important
You’ve now got a solid idea of what to expect with under-slab tunneling. Whether it’s a short dig or a long haul, most tunneling jobs wrap up in just a few days, with the plumbing and backfilling timeline layered on top.
At Anchor Foundation Repair, we’re efficient and experienced, and we’ll coordinate closely with your plumber to make things go as smoothly as possible. Once we get started, the only delays are ones outside our control, but we’ll work through them with professionalism and purpose.
Still curious about how tunnel backfilling works? Check out this related article to see how we make sure your home is safely and properly put back together:
👉 The Best Way to Backfill an Under-Home Tunnel + What If You Skip It