Is It a Slab Leak? 5 Symptoms Georgetown Plumbers Look For

Symptom 1: A warm spot on the floor

A hot-water line leaking under the slab heats the concrete above it, and that warmth transfers to whatever flooring sits on top. On a tile floor, the warm spot is often distinct enough to feel with bare feet, and on hardwood or laminate it can show up as a section that feels noticeably warmer than the surrounding floor. The warm spot typically appears directly above the leaking run, which makes it one of the most useful locating clues available before any detection equipment is used.

Cold-water slab leaks are harder to feel but can sometimes be detected as a cool or damp section of floor, particularly in a climate-controlled home where the floor temperature is otherwise uniform. Both types show clearly on a thermal camera, which maps the temperature across the whole floor in one scan and often reveals the extent of the leak's spread under the slab.

Symptom 2: An unexplained pressure drop

House-wide low pressure with no fixture to blame is one of the clearest diagnostic signals for a slab leak. When a line under the slab is leaking, it is losing flow before any fixture sees it, which means pressure drops everywhere at once rather than at one location. The drop is usually gradual, worsening over weeks as the leak grows, and it is often attributed to the city supply or the main shutoff before someone checks the slab.

The isolation test separates a slab leak from a main-line leak or a regulator problem. Close the main shutoff and watch whether the pressure improves. If it does, the problem is on the street side. If the pressure inside was already low and stays low with the shutoff closed, the loss is inside the house, and the slab is the first place to look.

Symptom 3: The water meter moves with everything off

A slab leak is a pressurized supply leak, which means it runs continuously regardless of what the fixtures are doing. The meter test, turning off every fixture and watching whether the leak indicator on the GUS meter keeps moving, catches this directly. A spinning or creeping indicator with the house fully shut down confirms an active loss in the pressurized system, and under a Georgetown slab-on-grade home, that loss is commonly in the buried supply line.

The rate of movement matters. A fast spin represents a significant flow, possibly a pipe that has failed at a joint. A slow creep represents a smaller pinhole leak that has been running for weeks or months. Either one should be found promptly, since the longer a slab leak runs, the more water it introduces under the slab and into the surrounding fill and foundation.

Symptom 4: Damp, cracked, or discolored flooring

When a slab leak runs long enough, the water it releases eventually finds a path to the surface. On a tile floor it shows as grout that stays persistently damp, tiles that crack or come loose as the mortar bed softens, or efflorescence, the white mineral residue that water leaves as it evaporates at the surface. On hardwood or laminate it shows as warping, buckling, or discoloration that spreads from a central point. On carpet it shows as persistent dampness that does not fully dry.

The extent of the surface damage is not a reliable guide to the size of the leak, because water under a slab travels along the path of least resistance rather than rising straight up. A relatively small leak can produce widespread surface moisture if the fill beneath the slab is permeable and the water has been traveling for weeks.

Symptom 5: A bill that climbs for no visible reason

An unexplained increase in the water bill, sustained over two or three billing cycles with no change in household use, is often the first symptom a Georgetown homeowner notices. The supply is leaving the system, but it is going under the house rather than through a fixture or a visible drip, so there is nothing to see. By the time the bill has climbed enough to be unmistakable, the leak has often been running for months.

Cross-referencing the bill with the meter test is what turns a billing suspicion into a confirmed diagnosis. If the bill is up and the meter is moving with everything off, a plumber with acoustic and thermal equipment can locate the source without opening the floor, marking the spot so the slab is cut only at the exact point the repair requires. That combination of a symptom read and a confirmed meter test is the foundation of every efficient slab-leak visit, and it is the sequence that protects the floor from cuts that were not necessary.