A hidden water leak in an Irvine home often shows up first on the water meter. IRWD advises turning off all water and checking whether the meter dial is still spinning. Other signs include a bill that jumps for no reason, a musty smell, stains or bubbling paint, and warm spots on a floor.
Start With the Water Meter Test
The meter is the cheapest leak detector you own. IRWD's advice for a bill that spikes is simple: turn off all water and check your meter to see if the dial is still spinning. If it moves with everything off, water is going somewhere.
The EPA's WaterSense program suggests a longer version. Read the meter, wait through a two-hour period when no water is being used, then read it again. Any change points to a leak.
A moving meter doesn't tell you where the water is going, though. It might be a toilet, an irrigation line, or a pipe inside a wall or under the slab. The rest of this guide is about narrowing that down.
A Water Bill That Climbs for No Reason
Compare this bill with the same month last year, not just last month. Summer irrigation alone can explain a jump. A rise in a cool month with no change in household habits is a stronger clue.
Small leaks add up. The EPA says the average household's leaks can account for more than 9,300 gallons of water wasted every year. IRWD says a leaking toilet can waste 40 gallons a day, and a running toilet up to five gallons per minute.
IRWD also says low water pressure can be caused by an undetected leak. If the shower suddenly feels weak and the meter moves with everything off, take both clues seriously.
Clues on Walls, Ceilings and Floors
Water inside a wall or ceiling has to show up somewhere. These are the signs we see most often before anyone knows there's a leak.
- Yellow or brown rings on a ceiling, especially under a bathroom or laundry room.
- Paint that bubbles, peels or feels soft along the bottom of a wall.
- Baseboards that swell, split or pull away from the wall.
- Wood or laminate planks that cup, lift at the seams or feel spongy.
- Grout that stays dark long after a shower, or tile that moves underfoot.
- A cabinet floor under a sink that's warped, stained or soft.
Water still spreading? We answer every hour of the day and night.
Call (949) 539-8184A Musty Smell With No Visible Mold
Smell often comes before any stain. The EPA's mold course says that if a building smells moldy, that's a reason to suspect mold even when none is visible. A damp, earthy smell in one closet, cabinet or corner usually means something nearby is staying wet.
The same EPA course lists where hidden mold tends to grow. Its list includes the back side of drywall, paneling and wallpaper, and the underside of carpets and pads. Those are exactly the places a slow leak keeps wet.
If the smell is there, the water source matters more than the smell. Cleaning the surface won't fix a pipe that keeps feeding the wall behind it. The EPA advises drying water-damaged areas and items within 24 to 48 hours to prevent mold growth. A leak that's run for weeks is well past that point.
Warm Floors and Running Water Under the Slab
Some leaks sit under the floor itself. A hot water line leaking under a slab can leave a warm patch you feel through tile or with bare feet. You might hear water running with every fixture off, or find carpet that's damp with no source in sight.
Other slab clues include a water heater that seems to run constantly and cracks that show up in tile or flooring. None of these proves a slab leak on its own. Together with a moving meter, they're worth a closer look.
Our page on slab leak water damage covers what happens after the pipe is found. That includes drying the slab and flooring once the line is repaired or rerouted.
Why Irvine Homes Leak Where They Do
The median housing unit in Irvine was built in 2002. Still, 16.4 percent of units were built in the 1970s and 14.9 percent in the 1980s. In homes that age, some supply lines, valves and fixtures may be original.
Water chemistry is the other local question. IRWD's 2026 Water Quality Report lists average total hardness of 214 and 293 ppm for local treated water. Imported water averages 236 ppm, and the report puts the range at about 12.5 to 17.1 grains per gallon. IRWD also says it uses chloramines to maintain a robust disinfectant in its drinking water.
Hard water leaves scale in water heaters, valves and fixtures. Any link between chloramine and pinhole leaks in copper pipe is a contested claim, not a settled finding. Our post on hard water, chloramine and pinhole leaks looks at what has and hasn't been shown.
Simple Checks Before You Call Anyone
A few checks take less than an hour and can rule out the easy causes. If they don't explain a moving meter, the leak is likely inside a wall, ceiling or slab.
- Put a few drops of food coloring in each toilet tank and wait 10 minutes. Color in the bowl means the tank is leaking.
- Run each irrigation zone and walk it, looking for broken heads and puddles that point to a cracked line.
- Check that the irrigation timer is set correctly, since IRWD notes that default settings can kick in after a power outage.
- Open the cabinets under every sink and look at the supply lines, shutoff valves and cabinet floor.
- Look around the base of the water heater and under the washer for drips, rust or staining.
How We Find a Leak Without Tearing Into Walls
When the easy checks come up empty, we look for water rather than guessing at it. On a water leak detection visit we combine the meter, pressure and the house layout with what the surfaces tell us.
Moisture mapping and thermal imaging shows where a wall or floor is wet behind the paint. A thermal camera picks up the temperature change from water or a hot line. Meters then confirm it, so any opening is small and in the right place.
Once the source is found and fixed, the wet materials around it still need drying. Our guide on what to do in the first hour after a leak covers the steps if water is already showing.
Questions readers ask
Look for stains, bubbling paint or swollen baseboards, and notice any musty smell. Then turn off all water and watch the meter. If it moves and nothing visible is leaking, the source is likely hidden.
Yes. IRWD says a leaking toilet can waste 40 gallons a day. The EPA's dye test is simple: a few drops of food coloring in the tank, then check the bowl after 10 minutes.
Often a warm patch on a tile or wood floor, or damp carpet with no visible source. You might also hear running water with every fixture off. A moving meter together with these signs is a good reason to call.
Not always, and rarely wide open. Meters and a thermal camera narrow down the wet area first, so any opening is small. Wet materials around the leak may still need drying or removal.
Fixing the leak stops new water, but the wall cavity, pad or subfloor may still be wet. The EPA advises drying water-damaged materials within 24 to 48 hours. A moisture reading tells you if anything is still wet.
Where these facts come from
- Irvine Ranch Water District: If Your Water Bill Spikes, Try This
- Irvine Ranch Water District: Meters and Leak Detection Resources
- US EPA WaterSense: Fix a Leak Week
- US EPA: Mold Course Chapter 2
- US EPA: A Brief Guide to Mold, Moisture and Your Home
- Irvine Ranch Water District: 2026 Water Quality Report
- Point2Homes: Irvine, CA Housing Market and Demographics