Most household leaks are quiet. A toilet flapper that seeps, a supply line dripping inside a cabinet or a pipe leaking under the slab can run for months before anything looks wrong. The good news is that you can confirm a leak yourself in an afternoon, with a flashlight, a few drops of food coloring and your water meter.
The EPA's WaterSense program says the average household's leaks can waste more than 9,300 gallons of water a year, and that 9 percent of homes have leaks wasting 50 gallons or more a day. LADWP puts it at up to 10,000 gallons a year per household. Here's how to find out if yours is one of them.
Signs you might have a water leak
None of these proves a leak by itself, but each one is a reason to run the tests below.
| What you notice | What it can mean | Test to run |
|---|---|---|
| Water bill went up and your habits didn't change | A running toilet, an irrigation leak or a hidden supply leak | Meter test, then the toilet dye test |
| Sound of running water or hissing when everything is off | A toilet refilling, or water moving through a pipe in a wall or under the floor | Meter test, then listen room by room |
| Toilet refills by itself between flushes | A leaking flapper or fill valve | Toilet dye test |
| Damp spots, stains or bubbling paint on walls, ceilings or baseboards | A supply or drain leak nearby, often below a bathroom | Meter test; check whether it gets worse when a fixture is used |
| Musty smell or mold that keeps coming back | Materials staying wet, often from a slow leak inside a wall or cabinet | Room-by-room walk-through |
| Warm spot on a tile or concrete floor | A hot-water line leaking under the slab | Warm floor check, then the meter test |
| Water pressure slowly dropped | Water escaping before it reaches the fixtures, or old pipe | Meter test |
| A soggy patch in the yard that never dries | The service line from the meter or an irrigation line | Meter test with the house shutoff closed |
The home tests, in order
1. The water meter test
This is the one test that settles the question. Turn off everything that uses water inside and out: faucets, toilets (let them finish refilling), the washer, dishwasher, ice maker, evaporative cooler and irrigation. Then find the meter, usually in a box near the curb or sidewalk, and look for the small leak indicator, often a triangle, star or little dial. LADWP says movement on the leak detection gauge with all the water shut off means you have a leak.
If the indicator isn't moving, write down the full reading and use no water for at least two hours. The EPA's tip is to check the meter before and after a two-hour period when no water is being used; if it changes at all, you probably have a leak. Our hidden water leak guide walks through the meter test in more detail, including what to bring and how to read the dials.
2. Split the house from the yard
If the meter moved, close your home's main shutoff valve (how to find and close it) and watch the meter again. If it stops, the leak is inside the house: a toilet, a fixture, the water heater, or a pipe in the walls or slab. If it keeps moving with the house shut off, the leak is between the meter and the house, or in irrigation that branches off before the shutoff.
3. The toilet dye test
Toilets are the most common silent leak. Take the lid off the tank and add a few drops of food coloring to the tank water, not the bowl. Don't flush. Wait about 15 minutes. LADWP says if the coloring seeps into the bowl without flushing, you have a leak that should be fixed. Usually it's a worn flapper, an inexpensive part; our guide to fixing a running toilet shows how to replace it. Test every toilet in the house, and flush afterward so the dye doesn't stain.
4. Check the bill against last year
Compare your current bill with the same billing period a year ago, so seasonal watering doesn't fool you. LADWP bills water in units of 100 cubic feet, which is 748 gallons, so a jump of a few units is thousands of gallons. The EPA suggests looking at a winter month: if a family of four uses more than 12,000 gallons a month in January or February, there could be serious leaks. A sudden jump with no new people, no pool fill and no new watering schedule is a red flag. Our high water bill checklist covers the other causes.
5. Listen when the house is quiet
Late at night or early in the morning, with everything off, walk the house and listen. Put your ear near walls behind toilets, sinks, the tub and the water heater, and near the main shutoff or a hose bib on the outside wall. A steady hiss or trickle with nothing running means water is moving. A toilet that briefly refills on its own every so often is a leaking flapper or fill valve.
6. Walk the house, room by room
- Under every sink: feel the supply lines, shutoff valves and drain with a dry paper towel. Look for warped cabinet floors, stains or rust on the valves.
- Behind and around toilets: check the supply line, the shutoff and the floor at the base. A soft or stained floor at the base can mean a failed wax ring.
- Water heater: look for water in the drain pan or on the floor, rust at the bottom of the tank, and drips from the relief valve's discharge pipe. If the tank itself is leaking, see signs a water heater is failing.
- Laundry: check the washer hoses for bulges or drips and the wall box behind the machine.
- Kitchen appliances: the refrigerator ice-maker line and the dishwasher supply are easy to miss. Look for swelling in the flooring or cabinet bases next to them.
- Walls and ceilings: look for stains, bubbling paint, sagging drywall or damp baseboards, especially on the ceiling under an upstairs bathroom.
- Smell: a musty smell that won't go away often means something is staying wet. The EPA says the key to mold control is moisture control, and that water-damaged areas should be dried within 24 to 48 hours.
7. Check for warm spots on the floor
Many San Fernando Valley and LA homes are built on a concrete slab with water lines under it. Walk tile or concrete floors barefoot, especially along the path from the water heater to the kitchen and bathrooms. A spot that feels warm, even at night, along with a water heater that seems to run more than it should, points to a hot-water line leaking under the slab. Our guide to slab leak warning signs covers the hot-line and cold-line checks. Don't start breaking concrete to look; a plumber can locate it first.
What your results mean
| Result | Likely location |
|---|---|
| Meter moves, stops when the house shutoff is closed | Inside the house: toilets, fixtures, water heater, or pipe in the walls or slab |
| Meter keeps moving with the house shutoff closed | The service line from the meter to the house, or irrigation that tees off before the shutoff |
| Meter moves and dye shows in a toilet bowl | At least one toilet is leaking; fix it and re-test, since there can be more than one leak |
| Meter moves and a floor spot is warm | Possible hot-water line leak under the slab |
| Meter is still, but there's a damp spot or stain | A drain leak or a leak that only happens while a fixture runs (a shower pan, a tub overflow, a drain joint); the meter can't see those |
If you find a leak
- Stop the water. Close the shutoff valve for that fixture, or the main shutoff if you can't isolate it.
- Protect your things. Move belongings, put down towels or a bucket, and if water is near outlets or a ceiling is sagging, stay clear of that area.
- Take photos of the spot, the meter readings and any damage before cleanup.
- Dry things out quickly. Fans and open cabinets help; the EPA's 24 to 48 hour window for drying is the reason not to wait.
- Call a plumber for anything inside a wall, ceiling, floor or slab, or for a leak in the yard line.
How a plumber finds a hidden leak
Professional leak detection starts the same way you did, with the meter, then narrows it down without opening walls or floors at random. Typical tools are acoustic listening equipment that picks up the sound of water escaping a pressurized pipe, thermal imaging to trace a hot-water leak through a floor or wall, moisture meters, and pressure tests that isolate the hot side, the cold side and individual sections of pipe. Once the spot is pinpointed, the repair can be a small, targeted opening. For leaks under the foundation, see slab leak repair; if an older line keeps failing in more than one place, repiping or water line replacement may make more sense than chasing leaks one at a time.
What leak detection costs in LA
These are published ranges from other LA-area plumbers and cost guides. They're a sanity check, not a quote. The repair itself is priced separately, after the leak is found.
| Service | Published range | Source |
|---|---|---|
| Electronic leak detection, LA & SFV | $150–$400 | A+ Electric & Plumbing |
| Leak detection, San Fernando Valley | $295–$595 | Last Drop Plumbing & Rooter |
| Leak detection, Los Angeles | $150–$500 | Plumbing Connection LA (cost guide) |
| Leak detection, Burbank | $200–$600 | PRO Plumbers of Burbank (cost guide) |
Rooter Pros gives free estimates on leak detection: call (818) 669-9019 and you get the price before any work begins, with flat-rate pricing and no overtime charges, day or night. Seniors, active military and veterans get 10% off; mention it when you call.
When to call a plumber
Call if the meter moves with everything off and you can't find the cause at a toilet or faucet, if the meter keeps moving with the house shutoff closed, if you find a warm spot on the floor, a stain or damp spot that keeps growing, or a musty smell you can't trace. Call right away for water coming through a ceiling or a wall. The longer a hidden leak runs, the bigger the water bill and the repair.
Meter moving and can't find the leak in Burbank, Glendale or the Valley? Rooter Pros locates hidden leaks in walls, floors, slabs and yard lines, and shows you where it is before anything is opened. Licensed & bonded (CSLB #917630), open 24/7, with free estimates, flat-rate pricing and no overtime charges.
Call (818) 669-9019Leak statistics and test steps are from the EPA WaterSense program, the EPA's mold guide and LADWP's published pages. Prices in the table are typical published ranges from other Los Angeles-area plumbers and cost guides as of November 2026; they are not Rooter Pros quotes and change over time. Sources are linked above.