What Is a Slab Leak? (And How to Spot One in Your Home)
So, What Exactly Is a Slab Leak?
A slab leak is a water leak that occurs in the pipes underneath the concrete foundation — or “slab” — of your home. Unlike a visible leak under your sink or behind your toilet, slab leaks are hidden beneath several inches of concrete and soil. That makes them difficult to detect without professional tools and training.
What Causes a Slab Leak?
- Corrosion in metal pipes: Most older homes use copper or galvanized steel piping, both of which are vulnerable to corrosion over time. Corrosion is a natural chemical reaction where the metal degrades — eventually forming pinhole leaks or cracks. This process is sped up in areas with hard water, acidic soil, or high water temperatures.
- Plastic or PEX pipe failure: Newer homes may have PEX or CPVC piping, which avoids corrosion — but these materials can still fail. Defects from manufacturing, extreme heat exposure, or shifting soil and foundation movement can all lead to cracks or punctures.
- Water pressure problems: Excessive water pressure — anything consistently over 80 psi — puts significant strain on pipes. Over time, this pressure can cause fittings to fail or pipe walls to burst, especially at weak joints.
- Foundation shifting and settling: Your slab sits on soil that expands, contracts, and shifts over time — especially in desert climates like Arizona. If the ground beneath your home moves, it can place tension on the pipes running through it, eventually causing them to bend, break, or disconnect entirely.
Why Slab Leaks Are So Serious
- Ruined flooring or carpets
- Mold growth inside walls or under the floor
- Structural weakening of the concrete slab itself
- Costly water bills before the leak is even found
How to Tell If You Have a Slab Leak
Expensive Water Bills
Most homes have consistent water usage month-to-month. A sudden jump in your bill — without any added water use — could be the first clue. If your bill keeps rising and you’ve ruled out obvious causes like:
- A running toilet
- A leaking faucet
- A broken irrigation line
…it may be time to check for a slab leak.
Low Water Pressure
If your sinks and showers aren’t flowing like they used to, and your neighbors aren’t experiencing the same thing, a leak in the main line could be the issue. Water pressure usually sits around 50–60 psi for residential homes. A slab leak reduces the volume and pressure of water reaching your fixtures.
Water on the Floor
One of the most noticeable signs is feeling or seeing water on your floors. Indoors, this might look like:
- Recurring wet spots
- Discoloration in tile grout
- Damp carpet or warped hardwood
- Warm or hot patches on concrete or tile
These areas may resemble pet accidents or spills — but if they keep coming back without a clear cause, it’s time to investigate deeper.
Moisture on the Outside of Your Foundation
In some cases, the water doesn’t rise through the flooring — instead, it may exit out the sides of your home’s slab foundation. If you notice damp spots or mold on the exterior base of your home, and it’s not related to sprinklers or rain, a slab leak could be forcing water out sideways.
Why You Need a Restoration (Not Just a Plumber)
When dealing with a slab leak, it’s not enough to simply fix the pipe — you also need to properly address the water damage it caused. Materials like tile, drywall, wood flooring, and subfloors can hold moisture for a long time, creating the perfect environment for mold growth. Left untreated, this moisture becomes a serious health hazard. That’s why you need more than a plumber — you need a professional water damage restoration team like Unified Restoration. We don’t just repair, we inspect, dry, and document all affected materials to ensure they meet industry-standard dry levels.
At Unified Restoration, we use:
- Thermal Imaging Cameras
- Non-invasive Moisture Detection Tools
- Over 40 Years of Water Damage Expertise
We don’t guess — we diagnose. And we’ll tell you the truth, not sell you on something you don’t need. Bonus: Slab leak restoration is often covered by your homeowner’s insurance policy. We can help guide you through the claims process.
Watch Real Footage From a Slab Leak Job
This real example from Southeast Phoenix shows what can happen when a slab leak goes undetected.
Want to learn how slab leaks are actually repaired? Click here for our step-by-step guide.
