5 signs you have a slab leak (and what to do next)
A slab leak hiding under your foundation can cause serious structural damage. These are the early warning signs — and why fast action matters.
Sandra Reyes Licensed Master Plumber 4 min read
What is a slab leak?
A slab leak is a leak in the water supply or drain lines that run beneath your home's concrete foundation. Because they are hidden under the slab, they can go undetected for months.
The 5 warning signs
Hot spots on the floor
If a section of your floor feels warm, a hot water line under the slab may be leaking.
Unexplained water bill spike
A sudden 20-40% increase in your water bill with no change in usage habits is a classic sign.
Reduced water pressure
If pressure has dropped throughout the house, water may be escaping before it reaches your pipes.
Foundation cracks or shifting
Water undermining the soil beneath your slab can cause settling and cracks in walls.
Mold smell without visible mold
A persistent musty smell near floors often means moisture is wicking up through the slab.
What to do
If you notice two or more of these signs, call a plumber for a pressure test and acoustic leak detection. Early detection typically means a simpler repair.
