A slab leak is a leak in one of the water pipes running beneath your home's concrete foundation, and you can usually spot one by watching for an unexplained spike in your water bill, the sound of running water when everything is off, warm spots on the floor, or low water pressure. In South Florida, these leaks are especially common in older slab-on-grade homes, and catching one early saves you from major foundation damage. Here is how to tell if you have one.
What is a slab leak?
A slab leak is a leak in a water supply line buried in or under the concrete slab your house sits on. Because the pipe is sealed beneath the foundation, water escapes silently into the ground or up through the floor. Left alone, a single slab leak can waste 10,000 or more gallons a month.
What are the warning signs of a slab leak?
The most common signs are a water bill that jumps with no change in usage, the sound of running water when every faucet is off, and warm or damp spots on the floor. You may also notice low water pressure, cracks in flooring or walls, or a mildew smell. Any one of these is worth investigating.
Sounds and floor temperature
If you hear faint running or hissing water with the main valve open but no fixtures in use, a hidden line is likely leaking. A hot water line leak can warm a section of tile or laminate, so an unexplained warm patch underfoot is a classic clue.
Water bills and pressure
A sudden, unexplained increase in your monthly bill is one of the clearest red flags. A leak under the slab also bleeds off pressure, so faucets and showers throughout the house may feel weaker than normal.
Why are South Florida homes prone to slab leaks?
South Florida has a large number of slab-on-grade homes built from the 1960s through the 1980s with original copper supply lines. Decades of contact with our humid, mineral-rich soil corrode that aging copper from the outside in, which is why these older homes see slab leaks more often than newer construction.
How do plumbers find a slab leak?
Plumbers locate slab leaks without tearing up your whole floor by using electronic listening equipment, acoustic sensors, and pressure testing to pinpoint the exact spot. This non-invasive leak detection approach isolates the leaking line so only a small area of the slab needs to be opened. Diamond Plumbing has handled professional slab leak detection and repair across South Florida since 1999.
What detection looks like
A technician first confirms the leak is under the slab, then narrows the location with acoustic and pressure tools. Once the spot is marked, repair options include rerouting the line, spot-repairing through the slab, or repiping, depending on the pipe's age and condition.
Can a slab leak fix itself?
No. A slab leak cannot fix itself and almost always gets worse over time. The constant moisture corrodes the pipe further, erodes the soil supporting your foundation, and can lead to cracked floors, mold, and structural damage. Because it is buried, a slab leak rarely stops on its own, so treat it as an emergency plumbing issue and call Diamond Plumbing right away.
How much does slab leak repair cost?
The cost depends on the leak's location, how the line is accessed, and whether the fix is a spot repair, a reroute, or a full repipe. There is no flat price, so the most accurate way to budget is to have a licensed plumber locate the leak and assess the pipe first. Diamond Plumbing provides upfront estimates before any work begins.
What to do if you suspect a slab leak
If you notice these signs, shut off your main water valve to limit damage and call a licensed plumber. Diamond Plumbing is a state-certified contractor (Florida license CFC1431243) available 24/7 to homeowners across Miami-Dade and Broward, including every plumber in Hollywood and Coral Gables job we take on. Fast detection keeps a small leak from becoming a foundation problem.
Frequently asked questions
How long can a slab leak go undetected?
A slab leak can run for weeks or months before you notice, because the water escapes underground. That is why subtle signs like a slightly higher bill, a warm floor spot, or faint running-water sounds matter so much. The sooner it is found, the less damage and water are lost.
Will my homeowners insurance cover a slab leak?
Coverage varies by policy. Many policies help with resulting damage, such as ruined flooring, while excluding the pipe repair itself. Check your specific policy and document the damage. A licensed plumber's detection report can support your claim.
Is a slab leak an emergency?
Yes. Because the water undermines your foundation and feeds mold growth, a confirmed slab leak should be addressed immediately. Shut off your main water supply and call Diamond Plumbing's 24/7 line so a technician can locate and stop the leak quickly.