How does a pipe under the slab fail?

Pipes beneath a slab can fail for several reasons: corrosion of metal pipes, abrasive contact where pipes rub against concrete, poor initial installation, shifting soil that stresses fittings, and thermal expansion. Copper, galvanized steel, and older polybutylene systems each have distinct failure modes. Failure may start as a pinhole leak or an active rupture. Because the pipe is encased in concrete, a leak often remains hidden until water migrates upward or laterally and shows itself on a floor or in a crawlspace.

What are common water leak signs on the slab?

Signs of a slab leak include unexplained increases in the water bill, damp or warm areas on a floor, discolored or buckling flooring, persistent sounds of running water with fixtures turned off, and mold or mildew odors. In some cases, you may see efflorescence or small cracks in a slab where mineral deposits form. These indicators are not definitive proof of a slab leak but often warrant further investigation by diagnostic services to confirm the source before invasive work begins.

Can spray testing locate a slab leak?

Spray testing can be part of a dye or tracer approach: a non-toxic dye or tracer gas is introduced into the plumbing system while technicians spray or inspect suspect areas on or near the slab. More commonly, active acoustic listening devices, pressure testing, electronic leak detection, and infrared thermal imaging are used. Spray or surface-applied methods are most effective when combined with pressure tests and listening devices, which together narrow the search area and reduce unnecessary slab removal.

What should you do when the floor shows wet spots?

If you notice wet spots on a floor, first shut off the main water supply to limit further damage and reduce the risk of mold. Document the affected area with photos, remove or elevate furniture and floor coverings as safe, and ventilate the area to slow secondary problems. Contact a qualified technician or local services experienced in slab leak diagnostics. Temporary containment, such as towels or buckets, can help, but direct plumbing repair and moisture remediation typically require professional tools and expertise.

When should a technician be called?

Call a licensed technician when you suspect a slab leak, especially if you observe persistent wet spots, a sudden spike in water usage, or structural signs like floor instability. A trained technician will perform a sequence of tests—pressure checks, acoustic surveys, thermal imaging, and targeted excavation if necessary—to pinpoint the leak. Choosing a technician experienced with slab issues and local services in your area helps ensure they know regional soil conditions and common building practices that affect repairs.

A well-planned repair strategy balances invasiveness, cost, and long-term reliability. Repair methods include spot repair by tunneling to access and replace the damaged pipe section, rerouting plumbing above the slab to avoid future concrete work, or full slab replacement in severe cases. Post-repair moisture mitigation and concrete restoration may be needed to prevent mold and restore structural integrity. Permits and inspections may be required depending on local codes.

Slab leaks can cause significant property damage if left unresolved, but timely detection and an informed approach to repair reduce long-term risk. Understanding how pipes fail, recognizing water-related signs on the floor, and working with qualified technicians and local services will help you address the problem efficiently while minimizing disruption to the building and occupants.