The most common slab leak symptoms in a home are unexplained water bill spikes, warm or damp floor spots, sounds of running water with fixtures off, and new cracks or moisture around the slab. A slab leak is a pressurized water line leaking beneath the concrete foundation, so you usually notice secondary clues rather than a visible pipe break. This issue can stay hidden while slowly damaging flooring and framing if not addressed. We often see and diagnose these signs for homeowners in and around San Anselmo. One technician tell is that a hot‑side leak sometimes creates a narrow warm trail you can feel barefoot across tile.
Look for these clear indicators:
- Water meter moves when all fixtures are off or bills jump without reason.
- Warm or damp floor areas, musty odors, or new mold growth.
- Hissing or running‑water sounds and reduced water pressure.
- New cracks in flooring, baseboards, or pooling along slab edges.
If you suspect a slab leak, turn off the main water valve and call a licensed plumber for leak detection.
Updated: 2026-08-28
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