How to Tell If You Have a Slab Leak

By the Plumbing Pros Sherman TX team Published February 11, 2026 · Updated August 19, 2026

The warning signs, in the order people usually notice them

Most slab leaks announce themselves quietly before they announce themselves loudly. The first thing many homeowners notice is a water bill that has crept up with no change in their habits, because a slab leak runs around the clock whether anyone is home or not. Close behind that is the sound of water moving inside a wall or under the floor when every tap in the house is off, which is worth listening for late at night when the house is quiet.

The more physical signs come next. A warm spot on the floor usually means the leak is on a hot water line, since the escaping hot water heats the slab above it. Flooring or carpet that stays damp in one area, a musty smell that will not clear, and new cracks appearing in walls or floors as the foundation reacts to the water are all later signs. By the time you see cracking, the leak has usually been going a while, which is exactly why the earlier and cheaper signals are worth taking seriously.

Why Sherman sits in slab-leak country

Slab leaks are not equally common everywhere, and Sherman's ground is a big part of why they happen here. The east and south sides of town, including the older housing near the courthouse square, sit on Blackland Prairie clay, which swells when it rains and shrinks in a Texas drought. A concrete slab poured on that clay flexes as the soil moves under it, and over years that movement stresses the copper lines and connections cast into the slab until one gives. That is the practical reason a Sherman homeowner should treat slab leaks as a real local risk rather than a rare event.

The newer west and north sides, where the sandier Eastern Cross Timbers soil takes over and much of the recent growth is happening, are steadier but not immune, because a fresh slab poured on graded clay fill still settles in its first years. Wherever your home sits, the takeaway is the same: if the signs above appear, the odds that it is a genuine under-slab leak are higher in Sherman than they would be in a town with stable soil, so it is worth confirming rather than waiting.

Confirming it without tearing up the floor

The meter test in the opening is the homeowner version, and it tells you that water is escaping but not where. Pinpointing the leak under a slab is where a professional comes in, and modern location is far less invasive than the horror stories suggest. Using pressure isolation to narrow down which line is losing water, along with acoustic listening equipment that hears the leak through the concrete, a plumber can mark the spot within a small area before any concrete is opened.

That accuracy is the whole point, because the cost of a slab leak is driven less by the repair itself than by how much floor has to be opened to reach it. Precise leak detection is what keeps the access hole to a single spot instead of a trench across the room, and it is why we always locate before we dig. Skipping that step to save an inspection fee usually costs far more in unnecessary demolition.

What to do once you suspect one

If your meter test points to a leak, the sensible order is to confirm the location, then decide on the repair approach based on what is found. A single leak on an otherwise sound line is often a spot repair, reached through one opening in the slab. A home with older piping that has already leaked more than once may be better served by rerouting the line or, in the worst cases, a whole-home repipe that ends the cycle rather than chasing the next failure.

The one thing not to do is ignore it. Water escaping under a slab has nowhere to go but into the soil and the foundation, and a slow leak left alone can contribute to foundation movement and eventually become a water damage problem inside the home. Catching it at the water-bill-and-warm-spot stage, rather than the cracked-wall stage, is the difference between a contained repair and a much larger one.

Slab Leak Detection questions, answered