Repairs
A warm patch on the floor and a meter that keeps ticking
Slab leaks announce themselves quietly: a warm floor, a running sound with every tap closed, a meter that never settles. Here is how the leak is confirmed, how it is found, and how the three repair options are chosen between.
The signs are consistent. The sound of water running with every tap closed. A warm patch on the floor that has no reason to be warm. A water meter still ticking after the house is shut down. Hot water that never quite gets hot. A bill that jumped without a change in habits. Any one of those alone can be something else. Two of them together, in a slab-on-grade house, and a pressurised line under the concrete is the first thing to rule out, not the last.
The meter test that settles it in twenty minutes
Shut every fixture in the house, including the ice maker and anything the irrigation controller might trigger, then open the meter box and watch the small low-flow indicator on the register. If it creeps at all over twenty to thirty minutes with nothing drawing water, something on your side of the meter is losing water. Next, close the cold inlet valve on top of the water heater and watch again. If the indicator stops, the leak is on the hot side. If it keeps moving, the loss is on the cold. That one extra step saves hours of listening in the wrong half of the house.
Why it is almost always the hot line
Homes built in Costa Mesa through the 1960s and 1970s were plumbed in copper supply with cast iron waste, and on a slab-on-grade build the supply runs go under the concrete. Costa Mesa’s median build year is 1972 and about 68 per cent of the housing stock predates 1980, which places most of the city squarely in that construction. Hot copper expands and contracts every time the heater cycles, and where it rubs against concrete, rebar or a rough sleeve it thins at that one point until it opens. Heat and velocity do the rest, which is why the hot line fails first and why elbows fail before straight runs.
How the leak gets located before anything is broken
Nobody should open concrete on a hunch. Electronic listening equipment picks up the hiss of pressurised water escaping and works it down to a small area of floor. Isolating the hot and cold circuits and putting a gauge on each proves which line is losing. On hot lines, a thermal scan of the floor often shows the plume before anything is heard. Where the picture is ambiguous, the line can be charged with tracer gas and the escape point picked up at the surface. The point of all of it is a mark on the floor you can see, agreed before a saw comes out of the van.
Three ways to fix it
Open the slab and repair the spot
The floor covering comes up, a small window is cut in the concrete, the failed section is cut out and replaced, then the slab is patched. It is the least disruptive to the rest of the plumbing and the most disruptive to the room you are standing in. It makes sense when the pipe elsewhere is in good condition and the leak is a single mechanical failure at a known point.
Reroute that one line overhead
The line under the slab is abandoned in place and a new run is taken through walls and the attic to the same fixtures. The concrete stays shut. This is usually the right answer when the leak is under finished flooring you cannot match, under a kitchen island, or anywhere the access hole would be worse than the repair. It also removes that line from the slab permanently, so the same run cannot fail again.
Repipe the house
When a house has already had two or three slab leaks, the pipe is telling you something about its condition rather than its luck. A repipe replaces the supply system above ground, typically in PEX to a manifold, and retires the under-slab runs entirely. It is the largest of the three and it is not the right answer for a first leak in otherwise sound copper. We do not push it there, and we say why.
What decides which one
Permits, and what happens to your floor
Repiping is permitted work through the city building department, and on unincorporated county land such as North Tustin, Rossmoor, Coto de Caza, Ladera Ranch or Rancho Mission Viejo it goes through Orange County instead. A single spot repair and a reroute are treated differently from a whole-house repipe, and the scope decides which applies. Plan the floor before the first cut rather than after: concrete gets patched back level and clean, but matching the finished surface over it is its own trade and its own lead time.
A drain-side leak under the slab is a different animal
Waste lines are not pressurised, so a broken cast iron drain under the slab will never move the water meter and cannot be heard the same way. It shows up as recurring backups from one fixture, damp at the base of a wall, a smell that comes and goes, or a hollow sound in one patch of floor. The only honest way to look at it is a camera in the line. That also tends to answer a second question at the same time, because on fifty-year-old cast iron the restriction is usually a lining across the whole pipe wall rather than a lump in the middle, which is why a snaked drain backs up again three weeks later.
Before the crew arrives
Photograph the meter register with the timestamp on, clear the floor in the rooms where you hear the sound, and note the times of day it is loudest. If you have a plumbing plan from the original build, a prior camera report, or paperwork from an earlier slab repair, put it on the counter. And if the leak is on the hot side, closing the cold inlet at the heater stops the loss overnight without shutting water to the whole house.