Much of San Jose was built on slab on grade foundations from the 1950s onward, with copper supply lines run in or under the concrete. When one of those lines fails, the water has nowhere to go but up through the slab or sideways under the flooring, and it can run for weeks before anybody notices anything worse than a warm spot on the floor.
- Warm floor spots, a running water meter with everything off, unexplained high bills, and the sound of water with all fixtures closed are the classic signs.
- Repair options are spot repair, reroute, or full repipe. The right one depends on pipe age and how many leaks you have had.
- Insurance commonly pays to access and repair the resulting damage but not to replace the failed pipe itself.
- Slab leaks are slow leaks, which is exactly the fact pattern carriers deny as gradual. Documentation matters more here than in a burst pipe claim.
How to tell you have one
- A warm or hot spot on the floor. The most recognizable sign, and it means the hot line is the one leaking.
- The meter moves with everything off. Shut every fixture in the house and watch the low flow indicator on the water meter. If it turns, water is going somewhere.
- Water bills climbing for no reason. Compare against the same month last year rather than last month.
- Sound of running water when nothing is on. Usually loudest at a wall near the failure.
- Flooring that cups, lifts, or discolors, or baseboard that stays damp, or a musty smell in one part of the house.
- Cracks appearing in the slab or in drywall, if the leak has been undermining soil for a long time.
If you see these, shut off the water at the main and call a plumber for leak detection. If flooring is already wet or there is any smell, call a mitigation crew at the same time. Supraclean answers 24/7 at (408) 216-0118.
Why San Jose houses get them
Postwar tract housing across San Jose sits on slab on grade with copper embedded in or beneath the concrete. Two things kill that copper. Abrasion, where the pipe rubs against concrete or rebar every time it expands and contracts with hot water, which is why the hot line usually fails first. And corrosion, from soil chemistry or from the interior of the pipe. Older galvanized supply lines have their own failure mode, corroding from the inside out on a predictable schedule.
None of that is a defect in your house. It is a material at the end of its service life, which is also why insurers scrutinize these claims.
Your three repair options
- Spot repair. Open the slab at the leak, cut out the bad section, repair it, patch the concrete. Cheapest and fastest. Reasonable for a young pipe with a single isolated failure, and a poor bet if the same line has already failed once.
- Reroute. Abandon the failed line in the slab and run a new line overhead through the attic and down the walls, or around through the walls. Avoids repeated concrete work, and it is often the right call for a single line in an otherwise sound system.
- Full repipe. Replace the supply system with copper or PEX run through walls and attic, abandoning everything in the slab. The most disruptive and the most permanent. If you have had multiple leaks, or the house still has original galvanized, this is usually the honest answer rather than paying for the same repair every eighteen months.
San Jose requires a plumbing permit for a repipe or water service project, and a concealed pipe replacement is treated as new work rather than an exempt minor repair. Get the permit. An unpermitted repipe surfaces during a sale, and then it is a much more expensive problem. That is the exact category of issue we clean up on our code violation and permit resolution work.
Then somebody has to put the floor back
This is the part homeowners underestimate. The plumbing repair is often the smaller half of the invoice. The larger half is everything around it: concrete cut and re-poured, flooring removed and replaced, baseboard, drywall where walls were opened, cabinets pulled and reset if the leak ran under a kitchen, and paint.
Flooring is where it gets expensive, because a slab leak rarely stays in one room. If your flooring is continuous through several rooms and the material is discontinued, you are choosing between an obvious patch and replacing the run to a natural break. That is a conversation to have while the scope is being written, not after demolition. We go through it in what flooring survives water damage.
The insurance angle, specifically for slab leaks
Two things to know. First, most policies pay to tear out and access the failed pipe and to repair the resulting damage, but do not pay to replace the pipe itself. Second, and more important: a slab leak is by nature a slow leak, and slow leaks are precisely the fact pattern carriers deny as gradual deterioration rather than sudden and accidental.
That makes documentation decisive. Keep the leak detection report, the removed section of pipe, dated photos of the damage, and your water bills showing when consumption jumped, which is often the best evidence of when the leak actually started. Report it the day you discover it, not after you have had the plumbing fixed.