Slab Leak and Hidden Leak Water Damage in San Bruno

A warm spot on the floor, a water bill that keeps climbing, a faint sound of running water when every tap is closed. Hidden leaks do their damage quietly. Our slab leak water damage San Bruno crews track down the wet areas, dry floors and walls, and handle repairs once the leak is fixed. Call and a crew is dispatched immediately.

How can you tell if a San Bruno home has a hidden leak under the floor?

Watch for warm or damp spots on the floor, cracked tile, cupping wood, a musty smell, a meter that spins with every fixture off, or an unexplained jump in your water bill.

Many homes in the flats of San Bruno, including parts of Belle Air, Lomita Park, Mills Park and Huntington Park, sit on concrete slabs with water lines running underneath or through the slab. Over time, those pipes corrode, shift with the soil, or rub against concrete until they leak. Because the water goes into the ground or up into flooring from below, the damage often spreads for weeks before anyone notices.

Signs of a Hidden Leak Under the Floor

• Warm spots on the floor, which point to a hot water line leak
• Damp carpet or a musty smell with no obvious source
• Cracked tile or grout lines that look darker than the rest
• Hardwood or laminate that cups, buckles or lifts
• Mold or mildew along baseboards
• The sound of running water when nothing is on
• Low water pressure throughout the house
• The water heater running more than usual
• A water bill that rises with no change in use

How to Check for a Leak Yourself

This simple test helps confirm whether you have a leak:

Step 1: Turn Everything Off

Shut off all faucets, toilets, the washing machine, dishwasher and irrigation.

Step 2: Check the Meter

Find your water meter, usually in a box near the sidewalk, and note the reading or watch the small leak indicator.

Step 3: Wait

Wait 30 to 60 minutes without using any water.

Step 4: Check Again

If the reading changed or the leak indicator moved, water is going somewhere, and a hidden leak is likely.

Leak Detection in San Bruno, CA

Leak detection in San Bruno, CA starts with finding where water is getting into the structure. The crew uses non-invasive tools to map the wet area before anything is opened up:

• Moisture meters to measure wetness in floors, walls and baseboards
• Thermal imaging cameras that show cool or warm spots where water is spreading
• Acoustic listening devices that pick up the sound of water escaping a pipe
• Hygrometers to check humidity in wall cavities and under flooring

Mapping the wet area first means only the smallest possible section of floor or wall has to be opened.

What Happens After the Leak Is Found

Pipe Repair

A plumber repairs the line by spot repair through the slab, rerouting it through walls or ceiling, or repiping the house. The right choice depends on the age of the plumbing and how many leaks there have been.

Drying the Slab and Floors

Concrete holds water for a long time. Dehumidifiers and air movers dry the slab, and flooring is lifted where needed to let it dry.

Wall and Baseboard Drying

Water from slab leaks wicks up into drywall and baseboards. These are dried or replaced depending on how wet they are.

Mold Prevention

Areas that stayed wet for weeks are checked for mold and treated.

Flooring Repairs

Once dry, damaged flooring is replaced or refinished.

Hidden Leaks Inside Walls and Ceilings

Hidden leaks are not always under the slab. Pipes inside walls, behind showers, under sinks and above ceilings can drip for months. Common spots in San Bruno homes:

• Behind showers and tubs with old valves
• Under kitchen and bathroom sinks
• Behind washing machines
• Around toilets with failing wax rings
• In walls shared with a bathroom in condos and townhomes

Galvanized and Copper Pipes in San Bruno Homes

Homes built in the 1940s and 1950s often still have galvanized steel water lines, which rust from the inside. Homes from the 1960s and later often have copper, which can develop pinhole leaks. If your home has had more than one leak, it may be worth asking a plumber about repiping. See burst pipe water damage.

Hidden Leaks and Hardwood Floors

A slow leak under hardwood can ruin a floor that has lasted 70 years. Caught early, floors can often be dried in place with specialized mats. See hardwood floor water damage.

Slab Leak FAQs

Slab Leak Repair Options Compared

Once a leak under the slab is found, a plumber usually recommends one of three approaches. Each has trade-offs.

Spot Repair

The plumber opens the floor directly above the leak, repairs the pipe and patches the concrete. It is the most direct fix, but it means cutting into flooring, and older pipes may leak again in another spot.

Reroute

The plumber abandons the leaking line under the slab and runs a new line through walls, the attic or the crawl space. It avoids breaking the slab and often makes future repairs easier.

Repipe

If several leaks have happened or the pipes are old galvanized, replacing the entire water supply system may be the most lasting fix. It costs more up front but removes the source of future leaks.

Whichever option you choose, the water damage around the leak still needs to be dried, and damaged flooring and drywall repaired.

Hidden Leaks in Condos and Townhomes

In condos and townhomes, a hidden leak in your unit can affect the unit below or next door, and a leak in a neighbor's unit can show up in yours. Shared walls with bathrooms and kitchens are common trouble spots. If you see a stain or smell mustiness on a shared wall, let your HOA or property manager know so both units can be checked. See condo water damage.

How Long Can a Hidden Leak Go Unnoticed?

Longer than most people think. A slow leak under a slab or inside a wall can drip for weeks or months before showing visible signs. During that time it can soak insulation, rot framing and grow mold. That is why watching your water bill and checking the meter once in a while are two of the simplest ways to catch a hidden leak early.

Hidden Leaks and Your Water Bill

San Bruno residents get water service from the city, so your bill is one of the best early warnings of a hidden leak. Compare your recent bills to the same months last year. A steady rise with no change in household use, new appliances or irrigation is worth investigating. Running a quick meter test with everything turned off takes less than an hour and can confirm whether water is leaking somewhere you cannot see.

Irrigation and Outdoor Leaks

Not every hidden leak is inside the house. Broken irrigation lines, leaking hose bibs and a damaged main line between the meter and the house can also waste water. Outdoor leaks can soften soil near the foundation and send water into crawl spaces and under slabs.

What to Expect During a Slab Leak Visit

The crew starts by asking about your water bill, any warm or damp spots, and when you first noticed a problem. Then they check moisture in floors and walls, scan with a thermal camera, and mark the wet area. You get photos and a clear explanation of what was found, what needs drying, and which areas may need flooring lifted. Once your plumber repairs the line, drying and repairs can begin.

Call About Slab Leak Water Damage in San Bruno

For fast help with slab leak water damage in San Bruno and hidden leak drying across 94066, call (650) 822-6798. A crew is dispatched immediately.

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