TL;DR

  • Slab leaks hide for weeks because the water disappears down through the slab into the soil below.
  • Five warning signs: warm spots on the floor, sound of running water with all fixtures off, unexplained high water bill, low water pressure, and damp baseboards or floor edges.
  • Slab leak detection is a plumber’s job — usually leak detection by acoustic, thermal, or pressure-decay testing.
  • Repair options: jackhammer through the slab, reroute through walls/attic, or epoxy line lining. Cost runs $1,200-$8,000 depending on approach.
  • Insurance usually covers the water damage and access; the pipe repair itself is often excluded.

Slab leaks are sneaky. Water leaks from a supply line buried in the concrete slab under your home, the soil absorbs most of it, and you do not see standing water inside the house until things have been wrong for weeks. The first time most homeowners notice is when the water bill jumps or a section of floor feels warm.

San Diego sees a lot of slab leaks because of when the housing stock was built. Tract homes from the 1970s through the 1990s — Vista, San Marcos, Escondido, Santee, much of Chula Vista — were built on slab-on-grade foundations with copper supply lines run through the slab. Those copper lines are now 30-50 years old. Pinhole corrosion is normal at that age. Soil chemistry, electrical grounding issues, and water chemistry all contribute.

The five warning signs

1. Warm spot on the floor

This is the textbook slab leak symptom for a hot-water-line failure. The hot supply line runs through the slab; it pinholes; hot water bleeds into the soil; the slab above warms up. You walk barefoot across the kitchen, hallway, or bathroom and notice a warm patch where there should not be one. Most often felt on tile or hardwood.

If you see this, mark the spot, take a photo with a thermal-camera app on your phone (most newer phones can do this with an FLIR attachment, or you can rent one), and call a leak detection plumber.

2. Sound of running water with everything off

Stand in a quiet part of the house with all fixtures off, the dishwasher off, ice maker off, and listen. If you can hear a faint sound of running water — a hiss, a whoosh, a gurgle — through the floor or walls, that is often a slab leak. Confirm by going outside to the meter: open the meter box, find the leak indicator dial (small triangle or dial that spins when water flows), and watch it. If it is moving with everything off, water is leaving the system somewhere.

3. Unexplained high water bill

A pinhole slab leak loses water continuously, usually 50-300 gallons per day depending on the hole size. Over a billing cycle, that adds 1,500-9,000 gallons to your bill. If your bill jumped 30-50% with no change in usage, the meter is telling you something.

4. Low water pressure

If the leak is on the cold or hot supply main, you may notice reduced pressure at fixtures — especially the ones farthest from the meter. Pressure can drop slowly enough that you adjust without thinking about it. A sudden drop is more obvious; a gradual one only registers when you compare to neighbors or a previous home.

5. Damp baseboards, floor edges, or warped flooring

Eventually a slab leak finds the path of least resistance — usually up through the concrete, into the bottom plate of an interior wall, then into the drywall and baseboard. By the time you see this, the leak has been running for weeks. Hardwood floors warp at the boards above the leak; tile may show grout discoloration; carpet can stay damp at the perimeter.

Confirming the leak

If you suspect a slab leak based on the signs above, the next step is leak detection — and that is a plumber’s job, not a restoration company’s. Three common methods:

  • Acoustic detection: highly sensitive microphone listens for the sound of water under pressure escaping through the leak. Works well for active hot or cold leaks.
  • Thermal imaging: catches the temperature differential from a hot-water leak as it warms the slab.
  • Pressure decay testing: isolates sections of the supply system, pressurizes them, and measures rate of pressure loss to identify which line is leaking.

A good leak detection plumber will narrow the leak to within a few feet, sometimes within a few inches. That precision matters because it determines the repair approach.

Repair options

Spot repair through the slab

Plumber jackhammers a 2-3 foot square through the slab, exposes the leaking copper, cuts out the bad section, and replaces it with new copper or PEX. After repair, slab is patched with concrete. Flooring above the spot has to be removed and replaced. Total cost typically $2,500-$5,000 including flooring repair.

Reroute through walls or attic

Instead of opening the slab, the plumber abandons the leaking line and runs a new line through the walls and attic to the same destination. The old line is left in place but no longer carries water. Less destructive to the floor, more drywall work needed. Total cost typically $1,800-$4,500.

Epoxy line lining

A liquid epoxy is forced through the existing copper line, coating the inside and sealing the pinhole from within. Less common in residential, more often used in commercial buildings. Cost typically $4,000-$8,000.

Whole-home repipe

If you have one slab leak in a 40-year-old copper system, the math sometimes favors a whole-home repipe with PEX through the attic. You spend more upfront but eliminate the next 5-10 leaks that would otherwise come over the next decade. Cost typically $6,000-$15,000 for a single-family home.

The right choice depends on the age of the system, how many failures you have already had, and whether you are planning to stay in the home long-term.

What insurance covers (and does not)

Most San Diego homeowners policies cover:

  • Water damage from the leak (drywall, flooring, contents)
  • Access — the cost of cutting into the slab or walls to get to the leak
  • Drying and restoration

Most policies do NOT cover:

  • The pipe repair itself (the “tear-out and access” is covered, the “repair the cause” usually is not)
  • Long-running leaks that show evidence of months of seepage (excluded as gradual damage)
  • Whole-home repipes done preventively

The faster you discover and report the leak, the cleaner the claim.

What we do on the restoration side

Once the plumber has stopped the leak, our job is the cleanup:

  1. Cavity drying — InjectiDry hoses through small drilled holes in the wall to dry the cavity without major demo
  2. Slab drying — concrete moisture mapping with hammer-drill testing or non-destructive scanning
  3. Cabinet base drying — when the leak was under a kitchen
  4. Flooring decisions — hardwood and tile saves are sometimes possible with fast response
  5. Antimicrobial application — to prevent mold growth in cavities

Total restoration timeline runs 5-10 days for a contained slab leak.

Bottom line

Slab leaks are predictable in older San Diego tract homes. The five signs above are the early warning. Catching one in week one rather than week six is the difference between a $3,000 claim and a $20,000 claim.

If you suspect a slab leak, call your plumber for detection first. Then call us for the cleanup. Both go on the same insurance claim. (858) 808-6055, 24/7 across San Diego County.