MAINTENANCE TIPS · May 7, 2026 · 6 MIN READ
5 Signs You Have a Hidden Water Leak (and How We Find It)
By Geovanny · Sigma Plumbing & Rooter
Hidden water leaks are the most expensive plumbing problem we run, because by the time you see them, the damage is done. Here are the five signs your home is leaking somewhere you can't see — and how leak detection actually finds it without tearing up your floor.
5 signs of a hidden water leak
1. Your water bill jumped for no reason
A 20%+ spike on one bill with no change in usage is almost always a leak. A pinhole in a slab line can run 24 hours a day without you ever hearing it.
2. Warm spots on a tile or concrete floor
Classic slab leak symptom — hot water is escaping under the foundation. Every day you wait, the soil under your slab erodes a little more.
3. The water meter spins with everything off
Turn off every fixture and appliance, then watch the meter for 10 minutes. If the dial is still moving, you have a leak somewhere between the meter and the house.
4. Sound of running water with nothing on
Especially at night when the house is quiet. A faint hissing or trickling sound in a wall or under the floor is a leak until proven otherwise.
5. Discoloration, bubbling paint, or mildew smell
A leak inside a wall usually shows up first as a yellow-brown stain at the bottom of the drywall, peeling baseboard paint, or a musty smell near a closet or bathroom wall.
How we find it without breaking your house
We don't guess and start cutting. Our leak detection process uses four tools, in this order:
- Pressure isolation test — confirms whether the leak is on the hot or cold side, and on the supply side or the drain side.
- Acoustic listening discs — high-sensitivity microphones pick up the sound of water escaping a pressurized line, even through 4" of slab.
- Thermal imaging — finds the temperature differential a hot-water slab leak makes through tile or carpet.
- Tracer gas — for the toughest leaks, a non-toxic gas mix that escapes through the break and is detected on the surface.
You only open what we mark. That's the entire point — most homeowners we help have lived in fear of "tearing up the whole floor." We pinpoint the leak to within an inch or two so the repair is one tile, not the whole room. More on our leak detection service page.
What it costs in Norwalk
Slab and wall leak detection in Norwalk and surrounding LA & OC cities typically runs $250–$650 depending on access and how stubborn the leak is. Repair is separate and quoted in writing before any work starts.
The longer you wait, the more it costs
A hidden leak doesn't fix itself. The damage compounds — wood rot, mold, foundation issues, ruined flooring. Call (562) 521-4995 the day you spot the symptom. Sigma Plumbing & Rooter answers 24/7 across Norwalk, Cerritos, Downey, Bellflower, Lakewood, Long Beach, La Mirada, and Whittier. Real reviews on our Google Business Profile — please leave one if we've helped you.
Frequently Asked Questions
How do you find a leak without tearing up my floor?+
Pressure isolation tells us which line is leaking, then acoustic listening discs, thermal imaging, and tracer gas pinpoint the spot to within an inch or two. You only open what we mark.
How much does leak detection cost?+
Most slab and wall leak detection visits in the Norwalk area run $250–$650. Repair is quoted separately in writing before any work starts.
Can a small slab leak really cause big damage?+
Yes. A pinhole leaking 24 hours a day erodes the soil under your slab and can cause foundation settling, mold, and ruined flooring within weeks.
Is reroute always cheaper than slab repair?+
For one isolated leak in an otherwise healthy line, repairing in place is usually cheapest. For a home with multiple corroded slab lines, a partial or full reroute is often the better long-term spend.
Have we helped you? Please leave a quick review on our Google Business Profile.