Under Slab Plumbing Repair
The leak is under 4 inches of concrete and the bids disagree about how to reach it. The tunnel vs breach trade, and how to sequence plumbing with piers.
By the Georgetown Foundation Guide editorial team · Updated July 15, 2026
The camera footage is unambiguous: a cracked cast iron drain, bellied and holding water, 30 odd feet in from the cleanout, somewhere under the hallway. Two bids follow. One wants to saw through the slab in the master closet. The other wants to dig a tunnel under the house from the back flower bed and never touch your floors. Same pipe, very different weeks for your household.
Two roads to the same pipe
| Slab breach | Tunnel | |
|---|---|---|
| Access | Cut through the slab from inside | Hand dug under the beam from outside |
| Life at home | Room out of service, dust, flooring loss | Household mostly undisturbed |
| Cost logic | Cheaper for one accessible spot | More per foot, wins on long or multiple repairs |
| Best fit | Single defect near an edge or in bare floor areas | Finished floors, occupied homes, bigger scopes |
A breach is direct: cut, dig, fix, pour back. Its price advantage shrinks fast when the leak sits under wood floors or tile you cannot match, since flooring restoration lands on your side of the ledger. Tunneling costs more in labor but preserves the interior, and crews can run a long tunnel to service several failures in one mobilization. Neither answer is standard; the right one falls out of where the defect sits and what sits above it.
The cast iron clock
Cast iron drains rust from the inside, thinning along the bottom channel where water runs, until cracks and channel failures arrive in bunches. If your camera report shows scaling and rough walls through the run, understand what that means: the system is aging as a whole, and this repair is a chapter, not the book. Budget conversations go better when everyone admits that early.
Sequencing with foundation repair
When a house needs piers and plumbing, order of operations protects the money. Lifting a foundation flexes everything beneath it, including drain lines, so the accepted sequence is: hydrostatic test first, then the structural lift, then retest, then repair what the retest shows. Repair the plumbing first and the lift may break your new work; skip the retest and nobody knows what the lift did.
One more sequencing detail earns attention: tunnels dug for plumbing later become part of your foundation's support picture. Insist the scope state how voids will be backfilled and compacted, and keep that paperwork with your foundation records.
What it costs, honestly
Published industry cost data for the Georgetown area spreads this work from $1,500 for a simple spot repair to $15,000 where long tunnels, multiple failures, or reroutes stack up. Scope drives everything: feet of tunnel, number of defects, depth of the line, and what the retest turns up after the first fix. Treat any bid priced before camera work as a placeholder, and see the cost guide for how plumbing scope interacts with pier budgets.
Before signing, ask each bidder three things: who digs (their crew or a sub), how backfill will be handled, and whether the price includes a post repair hydrostatic test. The answers separate plumbing companies that understand foundations from crews that just dig fast.
Questions homeowners ask
Hand dug access tunnels are standard practice and structurally uneventful when done right. The question that matters comes at the end: how will the tunnel be backfilled and compacted so the soil supporting your slab does not settle later. Make the answer part of the written scope.
Sometimes, partially. Texas policies often exclude the worn out pipe itself but may cover resulting water damage, and some cover the cost of accessing the leak through or under the slab. Policy language varies a lot, so read yours and ask the adjuster about access coverage specifically, with your test results in hand.
Camera the entire system before deciding. One bad joint in otherwise sound pipe justifies a spot repair. Corrosion showing up throughout a cast iron run means each fix is a down payment on the next failure, and a reroute or larger replacement can be the cheaper decade.
A single spot repair through the slab often runs a day or two plus retest. Tunnel jobs add days of digging before a plumber ever touches pipe, and longer reroutes stretch further. The retest at the end is not optional; it is your receipt.
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