A sprinkler line cracked underground, a water service line slowly seeping — hidden leaks wash soil out from under concrete silently, 24 hours a day, until the slab drops. How to catch the signs early, who fixes the leak versus the slab, and the order of operations that keeps you from paying twice.
Water by itself does not sink concrete. What sinks concrete is what moving water carries away: the fine soil particles — silts and clays — that make up the ground under your slab. A pressurized leak, even a small one, keeps water moving through the soil around the clock. As it flows, it picks up fines and carries them off, grain by grain. The coarser sand and gravel stay behind, but the fines were the glue holding the soil matrix together. What is left is a looser, weaker soil with growing voids in it.
Eventually the voids get big enough that the slab starts bridging across empty space. Concrete is strong in compression and weak in everything else — a slab spanning a void is a slab waiting for a reason to drop. One heavy vehicle, one saturated spring, and the bridge gives way. The slab drops into the void, often in a localized bowl shape directly over the worst of the washout.
This is a different beast from surface drainage problems. A downspout dumping at the slab edge (the usual suspect) is intermittent — it erodes during storms and irrigation. A pressurized leak is constant: it works in drought, in winter, at 3 a.m. That constancy is both the danger and the diagnostic clue. Settlement that keeps progressing through a dry August, in a neat localized bowl, with no obvious surface water source, should make you think "leak" before you think anything else.
The most common culprit in Salt Lake Valley suburbs. Lateral lines run shallow under lawns and sometimes under or alongside driveways and walkways. A cracked pipe, a broken head, or a failed joint can leak every time the zone runs — all summer long. Because many homes run irrigation on secondary water or a separate meter, the leak never shows up on the culinary water bill. If your settlement appeared or accelerated during irrigation season, start here.
The pressurized line from the city meter to your house often runs under the driveway — it was the shortest path when the house was built. A failing joint or pinhole leak here runs 24/7/365 at full pressure, and it is perfectly positioned to wash out the soil under the exact concrete you drive on every day. This is the leak that sinks driveways.
Smaller, but they fail often — freeze damage to an unprotected spigot, a slowly dripping connection inside the wall. The volumes are lower, so the damage is slower, but a spigot leaking into the wall cavity or down the foundation can undermine the porch slab or walkway right next to the house over a few seasons.
Those corrugated pipes carrying roof water away underground are great until they crack, separate at a joint, or clog — at which point they become an underground leak, injecting roof runoff directly into the soil under your slab during every storm. If your settlement sits downhill of a buried downspout line, inspect the line before you blame anything else.
No single sign is proof, but they stack. Two or more together means it is time for the meter test below.
Describe the settlement pattern — where it is, when it started, whether it is still moving. We will give you an honest read on whether it sounds like a leak, drainage, or plain consolidation — and who you should call first.
Before you call anyone, spend an hour on this. It is the same test plumbers start with, and it is definitive for pressurized leaks.
Meter moved? You have a leak; call a plumber with leak detection equipment. Meter steady? The pressurized side is likely fine — shift suspicion to irrigation (test by running zones one at a time and watching for soggy spots or geysers) or surface drainage. Either way, you have spent an hour and learned something a $200 service call would have told you.
This is the most expensive mistake in this article, so let it be blunt: do not lift a slab over an active leak. Lifting fills today's voids. The leak makes tomorrow's voids. Within a year or two you are paying for the same lift again — and the second time, the contractor will (correctly) tell you the first lift failed because the water was never fixed.
The correct sequence: find the leak (meter test, then plumber) → fix the leak (plumber or irrigation tech) → verify it is fixed (meter test passes, soggy areas dry out) → lift the slab (fills the remaining voids permanently). A reputable lifting contractor will ask about water sources at the estimate visit — if yours never asks, consider that a red flag (see how to choose a contractor).
The one exception is triage: if a settled slab is actively dumping water toward your foundation, a temporary regrade or quick partial lift to shed water can be worth doing while you schedule the plumber. Treat it as triage — buying time, not the fix.
Keep the trades straight and the project stays simple:
| Job | Who | What it costs |
|---|---|---|
| Find the leak | Plumber with leak detection equipment | A service call — get the price up front |
| Fix a water service line leak | Plumber | Varies widely by depth and method; get two quotes |
| Fix an irrigation line break | Irrigation tech or plumber | Usually the cheapest fix on this list |
| Lift the settled slab | Concrete lifting contractor | $500–$3,000 typical residential; see the cost guide |
| Prevent recurrence | You + the contractor | Drainage fixes; sealing joints after lifting (why sealing matters) |
Notice what this site does not do: quote plumbing. Leak repair pricing depends on depth, access, and method — that is the plumber's estimate to give. What we publish, and what you can hold a lifting bid against, is the lifting side: mudjacking at $3–$8 per square foot, polyurethane foam at $5–$25 per square foot, with most residential jobs landing between $500 and $3,000. The lifting quote should be itemized separately from any plumbing work, so you can see exactly what each trade costs.
One more money note: if a leak drove your water bill up, call your water provider and ask about a leak adjustment — many utilities offer a one-time bill credit when you document a repaired leak. It will not pay for the concrete work, but it takes some sting out of the plumbing bill.
The pattern tells the story. Bad surface drainage creates broad settlement along the drainage path — a whole strip of driveway sloping toward the downspout discharge point, for example. A pressurized leak creates a localized bowl: one section dropping in a rough circle or oval, often with the worst drop directly over the leak, while the surrounding concrete stays put. The meter test settles it definitively: if the meter moves with everything off, water is escaping underground somewhere. And the calendar helps too — surface-drainage settlement pauses in dry spells; leak-driven settlement keeps grinding away in August. If you are unsure, a plumber's leak detection visit costs far less than lifting the wrong problem. Our downspout and drainage guide covers the surface-water side.
You can, but you will pay twice — so do not. Lifting fills the void that exists today. An active leak keeps washing soil out, which means new voids form under your freshly lifted slab, and within a year or two you are paying for the same lift again. Every reputable lifting contractor will ask about water sources during the estimate visit; if yours does not ask, that is a red flag in itself (see how to choose a contractor). The correct order is non-negotiable: find the leak, fix the leak, then lift. The only exception is emergency triage — a slab actively dumping water toward your foundation can get a temporary regrade while you schedule the plumber — but treat that as triage, not the fix.
Yes — a normal water bill does not clear the suspect. Small leaks do not always move the bill enough to notice, especially on a large household's usage. Irrigation leaks are the classic invisible culprit: many Salt Lake Valley homes run irrigation on a separate meter or a pressurized secondary-water connection, so a cracked lateral line can run for a whole summer without ever appearing on the culinary water bill. And slow seepage from a failing joint may only lose a little water while still mobilizing fines. The bill is one clue, not the verdict — soggy strips, greener grass lines, the sound of running water, and a localized bowl pattern all count as evidence even with a flat bill.
If you suspect a leak, the plumber (or irrigation tech) goes first. Here is why: the lifting contractor cannot give you a meaningful quote until the water situation is resolved, because the scope depends on whether the soil will stay put after the lift. A plumber with leak detection equipment finds and fixes the source; then the lifting contractor assesses the remaining void and quotes the lift. Calling the lifter first just means paying for an estimate visit that ends with 'fix the leak and call me back.' If you are not sure whether it is a leak at all, start with the meter test in this article — it is free and takes an hour.
No. Fixing the leak stops the damage, but it does not undo it. The washed-out void under your slab is still there — empty space does not refill itself, and the slab does not float back up. What the repair buys you is stability: the ground stops getting worse, which makes the lift a permanent fix instead of a temporary one. Think of it like stopping a roof leak before replacing the ceiling drywall — the repair order matters, but both steps are still required. Once the leak is fixed, lifting fills the void and restores the grade in a single visit. See how concrete lifting works for the process.
Often not. Most leak repairs happen at the leak point, which is frequently at a joint, a connection, or an accessible section — not in the middle of your driveway. Plumbers can often excavate a targeted hole at the leak location, and for water service lines there are trenchless repair and replacement methods that avoid open trenching across the whole run. Irrigation lateral repairs are usually simple dig-and-replace at the break. Ask your plumber specifically about minimizing concrete disruption — and if concrete does need to come up, that is actually useful timing information for the lifting contractor, who can plan the lift around the repair. The two trades coordinate well when they are sequenced correctly.
You do not need to wait months — once the leak is repaired and the soil has had a chance to drain (usually days, not weeks), the lift can proceed. The old advice about 'letting the ground settle' applies to major excavation, not to a repaired pinhole leak. What matters is that the water source is verifiably fixed: the meter test passes, the soggy strip dries out, the sound of running water is gone. One practical tip: schedule the lifting estimate for a week or two after the plumbing repair, and tell the lifting contractor what was fixed and where. That history helps them probe the right areas and confirm the voids are stable before they fill them.