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Slab Leak Guide

How to Know If You Have a Slab Leak — and What to Do Next

A slab leak is a break in a water line running beneath your home's concrete foundation. The three most common warning signs are a water bill that spiked without explanation, a warm or damp spot on your floor, and the sound of running water when every faucet and fixture in the house is off. If you notice any one of these, don't wait — call a licensed plumber for professional detection before the leak weakens your foundation or drives water into your walls.

Gardner Plumbing Co. serves 25 cities across Riverside County, eastern San Bernardino County, and the Coachella Valley — including Murrieta, Temecula, Menifee, Riverside, Corona, Eastvale, Palm Springs, Palm Desert, Redlands, and Yucaipa. Call 24/7: (951) 246-4337.

Last Updated: June 2026

Gardner Plumbing technician using acoustic leak detection equipment to locate a slab leak beneath a Riverside County home's kitchen floor
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Warning Signs

7 Signs You Have a Slab Leak

Each one is a standalone indicator — you don't need all seven to have a problem.

  1. 1

    Your water bill spiked with no obvious cause.

    A water bill that jumps $50 – $200 in a single billing cycle, with no change in household usage, points strongly to a pressurized leak under the slab. Hot-water-line slab leaks are especially common in Riverside County because the hard water erodes copper fittings from the inside over time.

  2. 2

    You feel a warm or hot spot on your floor.

    Slab leaks on hot-water lines raise the temperature of the concrete directly above the break. Walk barefoot across tile, hardwood, or laminate and note any section that feels noticeably warmer than the rest of the floor. This is one of the most reliable self-diagnostic tests a homeowner can perform.

  3. 3

    You hear water running when everything is off.

    Turn off every faucet, appliance, and irrigation zone. Stand in a quiet room. A faint hissing or rushing sound — especially near exterior walls or in the center of the house — suggests water is moving through a pipe it shouldn't be.

  4. 4

    Your water pressure dropped suddenly.

    A pressurized line that's breached bleeds pressure before water reaches your fixtures. If your shower suddenly feels weak or faucets run slower than normal, a leak in the supply line — including under the slab — is a likely cause.

  5. 5

    You smell mildew in one specific area of the house.

    Water escaping a slab pipe wicks upward through concrete and subfloor. When it reaches organic material — wood framing, carpet pad, drywall — it creates the conditions for mold within 24 – 48 hours. A musty smell concentrated in one room, without a visible water source, is a red flag.

  6. 6

    Your flooring is buckling, cracking, or separating.

    Prolonged moisture from a slab leak softens the subfloor and causes tile grout to crack, hardwood planks to buckle, or carpet to develop damp patches. If the damage appears in a pattern — along one wall, in one corner — trace it to the nearest plumbing run.

  7. 7

    You notice cracks in walls or a door frame that no longer closes squarely.

    Water under a slab changes the soil's load-bearing capacity. In Riverside County, where expansive clay soil is common in cities like Menifee, Perris, and parts of Corona, even a slow leak can shift a slab enough to crack drywall or rack a door frame. Foundation movement is a late-stage symptom — if you're here, call today.

Act Now

What to Do in the Next Hour

  1. 1

    Check your water meter with everything off.

    Locate the meter at the street. Turn off every faucet, toilet, appliance, and irrigation zone inside the house. Watch the meter's low-flow indicator (a small triangle or dial) for 60 seconds. If it moves, water is flowing somewhere — likely a leak. Take a photo of the meter reading, wait 30 minutes without using any water, then check again. A rising number confirms a leak.

  2. 2

    Note exactly where the warm spot or damp area is.

    Walk the perimeter and interior of the house. Mark the spot with a piece of tape. When a technician arrives with acoustic detection equipment, your observation cuts the diagnostic time from 2 – 3 hours to under an hour. Specific location data matters.

  3. 3

    Shut off the water to that zone if you know how.

    If you have individual shut-offs under sinks or at the water heater and the warm spot is near the hot-water side of the house, shutting off the water heater supply can slow the leak. If you're not certain which valve controls which line, shut off the main supply at the street. A few hours without water is far less expensive than a flooded subfloor.

  4. 4

    Call for professional leak detection — don't dig, don't drill.

    Slab leaks require acoustic listening equipment, electronic amplification, and sometimes thermal imaging to locate accurately. A homeowner breaking concrete to find a leak they heard "somewhere over there" regularly causes $3,000 – $6,000 in unnecessary repair costs. Detection technology narrows the break to a 12-inch section. Call Gardner Plumbing Co. at (951) 246-4337 — 24/7 emergency dispatch is available.

The Math

Slab leaks get more expensive by the week.

Detection + Spot Repair

$1,500 – $4,000

Acoustic detection isolates the leak to one foot

Ignore It 90 Days

$8,000 – $20,000+

Full repipe, flooring replacement, mold remediation

Precision Detection

How Gardner Detects Slab Leaks Without Jackhammering Your Whole House

Acoustic listening equipment

A trained technician presses a ground microphone against the slab surface and listens for the distinct frequency of pressurized water escaping a pipe.

Electronic amplification

Correlators compare the arrival time of the leak sound at two access points, calculating the exact distance from each end. This isolates the break to within a foot.

Thermal imaging

On hot-water line breaks, an infrared camera reads the temperature differential in the slab surface. Warm moisture traveling upward creates a visible heat signature.

Pressure testing

The suspected line is isolated and pressurized with nitrogen. A pressure drop confirms the leak is on that section, not elsewhere in the system.

Thermal imaging scan of a kitchen floor showing a warm-spot heat signature from a hot-water slab leak beneath the concrete foundation

Thermal Imaging in Action

Warm spot = pressurized hot-water leak beneath the slab.

Gardner Plumbing technician performing acoustic slab leak detection on a Riverside County home kitchen floor

On-Site Detection

Isolate the leak to within a foot before any concrete comes up.

What It Costs

What Does Slab Leak Repair Actually Cost?

Gardner Plumbing Co. gives you a written estimate before any work begins — three repair paths depending on what the detection finds.

$250 – $450

Step 1 — Detection

Pinpoint the Leak

Acoustic listening, electronic amplification, pressure testing, and a written estimate before any work begins. Gardner isolates the leak to within a foot before any concrete comes up.

$1,500 – $2,500

Repair Option A

Spot Repair

Targeted section of pipe exposed, damaged section cut out and replaced, concrete patched. Best for a single isolated break on an otherwise sound pipe.

$2,000 – $4,000

Repair Option B

Pipe Reroute

New supply line run above the slab — through walls or ceiling — bypassing the under-slab pipe entirely. Best when multiple failures suggest the buried line is at end of life.

$3,000 – $5,000+

Repair Option C

Epoxy Pipe Lining

A resin liner pulled through the existing pipe, sealing the interior without excavation. Not appropriate for all pipe sizes or materials — the detection determines candidacy.

Most standard homeowner's insurance policies cover water damage from a slab leak but not the pipe repair itself. Gardner Plumbing Co. provides detailed documentation for insurance claims. See our guarantee for written commitments on every job.

FAQ

Slab Leak Questions Answered

Questions & Answers

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What customers wrote about Gardner Plumbing's transparency, follow-through, and quality on complex jobs.

Cold-Water Valve Repair (Return Visit)

We have used this company multiple times over the past year because we trust them, and they continue to earn that trust every time. Most recently, they repaired a broken cold-water valve in our laundry room. During the installation, an unexpected issue came up because the new laundry box was configured differently than the original, which affected the condensate drain line from our upstairs A/C. Once the issue was identified, they returned promptly, took the time to understand exactly what was happening, and implemented a proper solution. What really stands out to us is how they handle situations when something unexpected comes up. No company is perfect, but this team stands behind their work and makes things right. That level of professionalism is hard to find.

Victoria B.

Riverside County, CA
Technician: Gardner Plumbing Team

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