7 Signs of a Slab Leak in Your Florida Home

By the Leak Detection Clermont FL team · Published 20 October 2026 · Updated 20 October 2026

A slab leak is a pressurised water line leaking under your home's concrete foundation. It rarely announces itself with a flood. Instead it whispers — a floor that feels oddly warm, a bill that creeps up, a faint sound of water at 2 a.m. In Florida, where most homes sit directly on a slab and the soil underneath is sand, those whispers matter: water escaping under the slab does not pool where you can see it, it drains away and quietly erodes the ground your foundation rests on. These are the seven signs of a slab leak that Clermont homeowners report most often, in roughly the order they tend to appear.

1–2. Warm spots and damp or swollen flooring

Run your hand — or walk barefoot — across tile, wood, or vinyl floors. A hot water line leaking under the slab heats the concrete above it, so one patch of floor feels noticeably warmer than the rest, often in a hallway, kitchen, or bathroom path where hot lines run. Cold-line leaks show up differently: flooring that feels damp or cool, laminate edges that swell and lift, carpet that stays dark in one spot, or grout that never fully dries.

Neither sign appears on day one. A pinhole leak can run for weeks before enough heat or moisture works through the slab and flooring, which is why the location of the warm or damp patch matters — it usually sits within a few feet of the leak itself and is one of the first clues a detection specialist uses.

3–4. Water sounds and the smell of mildew

Stand in a quiet house with every tap, appliance, and irrigation zone off. If you can hear a faint hiss, trickle, or running-water sound through a wall or floor, water is moving somewhere it should not. Under-slab leaks are a leading cause, because the pipe is pressurised around the clock — the sound does not stop when you stop using water.

The companion sign is smell. Moisture trapped under flooring and in the bottom plates of walls feeds mildew long before anything is visible. A musty odour that concentrates in one room, returns after cleaning, or is strongest near floor level deserves the same suspicion as a visible stain — especially alongside any of the other signs on this list.

5–6. Cracks, and pressure that is not what it was

Hairline cracks that suddenly appear in floor tiles, grout lines, baseboards, or the drywall just above them can mean the slab's support is changing. Escaping water washes sandy Florida soil out from under the concrete; the slab settles into the void by fractions of an inch, and rigid finishes like tile are the first to show it. One cracked tile can be an accident. A line of new cracks across a room is a pattern.

Low water pressure belongs on the list too, with a caveat: a single small pinhole rarely drops pressure noticeably. Pressure loss across several fixtures, or pressure that fades over weeks, suggests a larger break or a leak that has grown — and it is a reason to move this from 'watch it' to 'book the test' this week.

7. The water bill — and the meter test that settles it

The sign that finally pushes most homeowners to act is financial: a water bill meaningfully higher than the same period's normal, with no new pool, guests, or irrigation schedule to explain it. A slab leak runs 24 hours a day, so even a modest one — a gallon every few minutes — adds thousands of gallons a month.

You can confirm water is escaping before anyone visits. Turn off every tap and water-using appliance, make sure irrigation is off, then watch your water meter for 15–30 minutes. If the dial or the small leak-indicator triangle keeps moving, water is leaving your system somewhere. That test cannot tell you the leak is under the slab — but combined with warm floors, sounds, or smells, it makes slab leak detection the obvious next step. Our full guide to why a water bill suddenly jumps walks through the other suspects.

What happens if you wait: the cost of a month's delay

Homeowners often watch a suspected slab leak for a month to 'see if it gets worse.' It will — and the delay is rarely free. A leak passing even one gallon every ten minutes loses roughly 4,300 gallons a month, every gallon billed, while it softens and carries away the soil supporting the slab. Flooring damage spreads from the first damp patch outward, and mould colonises wet drywall and timber quickly in Florida humidity — the U.S. EPA's leak guidance exists precisely because ordinary household leaks quietly waste around 10,000 gallons a year in the average home, and a slab leak is not an ordinary, visible leak.

Waiting also weakens your own evidence. A bill history showing a sudden jump, followed by prompt detection and repair, is a clean story for an insurer or a utility adjustment request. The same jump followed by months of inaction invites the argument that the damage was avoidable. If two or more signs on the checklist are present, the cheapest week to act is this one.

Slab leak checklist: how many do you have?

• A warm, damp, or swollen patch on hard flooring
• Running-water sounds when everything is off
• A musty or mildew smell fixed in one room
• New cracks in tiles, grout, baseboards, or drywall
• Pressure dropping across several fixtures
• A water bill up with no change in usage
• A water meter that moves with the house shut down

Why Clermont slab homes are prone to this

Most of Clermont's housing — the 1990s–2000s slab homes in Kings Ridge and Summit Greens, the family homes in Legends and Greater Pines, and much of the newer construction south of Highway 50 — runs its supply lines under the slab. Those lines are now reaching the age where copper pinholes and fitting failures start, and Clermont's sandy soil hides the evidence longer than clay would: the water drains down instead of surfacing. That combination — ageing under-slab lines plus soil that conceals them — is exactly why the seven signs above, taken together, are taken seriously here. A slab leak detection visit uses acoustic listening and thermal imaging to pinpoint the leak through the concrete, so a repair opens the smallest possible area of floor.

Sources and further reading

U.S. EPA WaterSense — the facts on leaks and how to check your meter

Signs of a Slab Leak — FAQs