Your slab is a hiding place for water

Most houses in Bexar County sit on a concrete slab. Supply lines were placed in the pad, under the pad, or in a sleeved run that later filled with mineral and dirt. When a line weeps, water does not fountain through the living room. It travels along the bottom of the concrete and appears as a warm hallway, a soft toe-kick, or a bill that no longer looks like your family.

Post-tension slabs add a second rule: the cables in the concrete are not suggestions. Random jackhammering is how people turn a plumbing leak into a structural event. Mapping and caution are not upsells. They are the difference between a small opening and a tendon you cannot put back.

Clay soils around San Antonio swell when they wet and shrink when they dry. A leak under a slab is a local watering system. Some homeowners only notice a new crack in sheetrock months later and blame the weather. Weather is real here. So is a pressurized line that has been hissing since Thanksgiving.

The useful test is boring. Turn off every fixture, including ice makers and the irrigation controller. Look at the meter. If it still moves, something pressurized is open. Close the house valve. If the meter stops, the leak is on the house side. If it keeps moving, look at irrigation or the service before the house valve. That test is on the leak detection page because it belongs before anyone talks about tile.

Hot-side leaks announce themselves as a warm path. Cold-side leaks are quieter. Both can feed mold in cabinets. Neither is solved by painting the baseboard.

Reroute versus spot repair is a finish conversation as much as a plumbing one. Opening a new wood floor in Stone Oak is a different cost than opening a utility closet in a 1960s ranch. We would rather say that in daylight than pretend every slab leak is a two-hour patch.

Neighborhoods near Mission San José have older copper stories. North-central tracts have more PEX stories. The geology lecture stays the same: the slab hides the evidence until money or moisture forces a look.

If water is actively flooding, shut it down and use the emergency path. If you only have a bill and a hunch, start with detection. The slab leak page is the repair conversation that should follow a find, not precede it.

Official building questions go to San Antonio Development Services when you are in the city. We will not invent a license number to decorate this article. Check credentials at TDLR.

Stock photographs in this article are not job photos. There is no “after” picture of your hallway on this domain, and we will not fake one.

People delay slab work because the floor looks expensive. Delay waters the clay. If you need a week to choose between reroute and opening, keep the house valve closed. Borrow water. That sentence is unkind and also cheaper than a wider wet path under new wood.

Post-tension drawings, if you have them, are gold. If you do not, say so. We treat unknown tendon locations as a reason to map, not a reason to swing. A small, correct opening beats a confident hole in the wrong beam pocket.

If a foundation company is already measuring cracks, tell the plumber. Moisture is one input they watch. The two trades do not need to become one company. They do need to stop watering the pad while someone is trying to read it.

Warm floors in August can be sun. Warm floors in a snake shape at 10 p.m. in January are not sun. Trust the shape. Then isolate the meter. Then decide whether you are on a detection visit or an emergency shutoff. Those are sequential, not optional.

Tile match is the reason people wait. Waiting is the reason the match gets harder. If you need time to choose a reroute, close the valve. Living on bottled water for two days is ugly and still cheaper than a wider wet path under a floor you loved.

Bexar County clay does not need a lecture. It needs the water off. Every extra day of a pressurized leak is a local irrigation system you did not ask for. That is the whole argument for treating a hiss as urgent even when the rug still looks fine.

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