Plumbers often detect slab leaks by turning off the water, pressurizing the lines with air and using special equipment to listen for the escaping air. However, most homeowners first notice the problem as a wet or warm spot on the floor or when they receive an abnormally high water bill.
Slab leaks waste water and cause damage to foundations. The leaking water erodes the soil that supports the home and allows the collapse of a portion of the foundation. The collapse can case major damage to the home. In areas where soils expand when wet, the expanding soil lifts the home in the area around the leak before erosion, but the damage is similar.
Slab leaks occur in both the pressurized fresh water supply for the home and the drain system. In the pressurized system, water often leaks through small pinholes that develop due to corrosion of the pipe. Sewer system leaks are not under pressure, but occur when pipes separate at the joints. Sewer leaks are often more difficult to detect.
In some cases, the plumber suggests repairing the slab leak by breaking through the concrete floor to access the pipe. If there are numerous leaks, he may suggest rerouting the pipe to bury it outside the foundation of the home and abandoning the leaking pipes.