The most reliable signs of a hidden leak are a water bill that climbs without a change in habits, a water meter that keeps moving with every fixture off, warm spots on a slab floor, musty odors, and paint or flooring that bubbles or warps. Any one of these deserves a check; two or more usually means water is escaping somewhere you can't see.
- Your water meter is the best leak detector you own — if it moves with everything off, water is leaking.
- EPA data shows about 10% of homes have leaks wasting 90+ gallons per day.
- Warm spots on the floor are the classic sign of a hot-side slab leak, common in older Valley homes.
- Musty smells and bubbling paint mean moisture is already collecting in walls or floors.
- Small leaks grow — early detection is the difference between a repair and a restoration project.
What are the warning signs?
- A climbing water bill with no change in household habits.
- The meter test fails: with every fixture off, the meter's low-flow indicator still spins.
- Warm spots on the floor — hot-side slab leaks radiate heat up through tile and laminate.
- The sound of running water when nothing is on.
- Musty, earthy odors in one room, closet, or cabinet.
- Bubbling paint, warped baseboards, or lifting flooring.
- Low water pressure at fixtures that used to run strong.
How do I run the water meter test?
Turn off every fixture and water-using appliance, including ice makers and irrigation, then close the house-side main valve. A plumber can then run a meter test: if the utility meter's low-flow indicator still moves with everything off, water is leaking — and isolating the house main shows whether the leak is in the house plumbing or in the yard line between the meter and the house. The meter box itself belongs to the water utility, so leave opening it to the pros.
What should I do if I suspect a leak?
Don't open walls on a hunch. Professional leak detection uses acoustic listening equipment, pressure testing, and thermal imaging to pinpoint the leak before anything is cut — so the repair opening is inches wide, not feet. Our plumbing repair team locates and fixes hidden leaks across the Valley, and if the piping itself is at end of life we'll lay out repiping options honestly, with photos of what we found.
About this guide
From the Good News Plumbing & Drain Inc. team — family-owned and serving the San Gabriel Valley since 2001. California C-36 License #906746 (verify it at cslb.ca.gov), bonded & insured, and backed by our satisfaction guarantee. Guidance reflects the plumbing we repair and install across the Valley every week. Last reviewed July 16, 2026.
Sources & standards
Common questions
How much water can a small leak really waste? +
Per EPA WaterSense, the average household's leaks waste nearly 10,000 gallons a year — about the water needed for 270 loads of laundry — and one in ten homes leaks 90+ gallons a day. Even a slow drip adds up on your bill.
What is a slab leak? +
A leak in the water lines that run beneath a home's concrete foundation. Warm floor spots, the sound of water under the slab, and unexplained meter movement are the classic signs. Repair options range from a spot repair through the slab to rerouting the line overhead.
Will my homeowner's insurance cover a hidden leak? +
Policies vary — many cover sudden water damage but not long-term seepage or the pipe repair itself. Document everything with photos and call your insurer early. We provide written findings you can submit with a claim.
