The most reliable test for a hidden leak is the water meter. Turn off every faucet, appliance and irrigation line, then watch the meter. If the leak indicator or dial keeps moving, water is going somewhere it shouldn't. After that, look for stains, bubbling paint and warped baseboards, listen for running water when nothing is on, and pay attention to musty smells in closed rooms.
Start With the Meter
A hidden leak is still a leak, and the meter counts it.
- Make sure nothing in the house is using water: faucets, toilets, the washer, the dishwasher, the ice maker, a water softener that might be regenerating, and the sprinklers if they run on the same supply.
- Find your water meter and note the reading. Many meters also have a small leak indicator, often a little triangle or star-shaped dial, that spins with even a slow flow.
- Wait without using any water. A short check of fifteen minutes shows a fast leak; leaving it for a couple of hours, or overnight, catches a slow one.
- Read it again. Any change means water is flowing somewhere.
If the meter moves, close the main shutoff inside the house and check again. If the meter stops, the leak is inside the house. If it keeps moving with the main closed, the leak is on the service line between the meter and the house, which is a plumber's job.
For Layton customers: Layton City lets utility customers view their billing and water usage history online. A usage figure that has crept up month after month, with no change in how the household uses water, is worth taking seriously, especially through the winter, when sprinklers aren't running.
What You Might See
- A stain on a ceiling or wall that slowly grows, often with a darker ring at the edge
- Paint that bubbles, blisters or peels in one spot
- Baseboards that swell, separate from the wall or turn dark at the bottom
- Drywall that's soft when you press it near the floor
- Laminate or hardwood that cups, buckles or lifts at the seams
- Grout that stays dark long after a shower, or tiles that loosen on a wall shared with plumbing
- A ceiling that looks slightly lower in one area, which can mean water is pooling above it
What You Might Hear
With the house quiet and nothing running, stand near walls that carry plumbing: the wall behind a bathroom, kitchen or laundry room, or the wall below an upstairs bathroom. A hiss, a steady trickle or a drip that keeps going when no fixture is on points to a leak. A toilet that refills by itself every so often is usually leaking internally into the bowl rather than into the wall, which wastes water but doesn't damage the house.
What You Might Smell or Feel
A musty smell in a closet, a basement room or a bathroom that wasn't there before often means something behind the surfaces has stayed damp. In a basement with a slab floor, a warm patch on the floor can point to a leak on a hot water line under the concrete. A water heater that seems to run more often than it used to can also mean hot water is leaking somewhere.
Where Hidden Leaks Usually Start
Most hidden leaks come from places people rarely look:
- supply connections behind the toilet and under the vanity
- the shower or tub valve inside the wall
- the washer hookups and the box they sit in
- the ice-maker line behind the refrigerator
- the dishwasher supply and drain under the kitchen counter
- fittings on lines in exterior walls that froze and partly cracked during a cold snap
That last group catches people out after a hard freeze, because a cracked fitting can hold for days before it starts weeping. Will PEX burst if it freezes? covers where freeze damage tends to show up later.
Leaks That Only Show Up in Winter
Some hidden leaks follow the seasons. A supply line in an exterior wall that partly cracked during a cold snap may only weep when the wall warms and cools each day, so a stain appears, dries, and appears again. A frost-free spigot that split over winter stays silent until someone opens it in spring. And a sprinkler line or backflow device that froze leaks only once the sprinkler supply is turned back on. If a stain comes and goes with the weather, or appears the first time an outdoor fixture is used each year, that pattern is a strong clue. Why a frost-free spigot can still split covers the spring version of this problem.
If You Find One
Close the nearest fixture valve or the main shutoff to stop the flow. Take photos of what you can see. Don't paint over stains or close up anything you've opened until you know the material behind it is dry, because a wall that looks fine on the surface can still be holding water inside.
A hidden leak is often only discovered after the water has spread through a cavity, so the damage is usually wider than the stain suggests. A cleanup contractor uses a moisture meter and a thermal camera to trace how far it went, then opens and dries what needs it. Ceiling and wall water damage explains how that works, and if the smell is the main symptom, mold checks after a leak covers what happens next.
Found something in a Layton wall or ceiling? The number for ZIP 84040 and 84041 is (801) 788-4740; it routes to a local cleanup contractor, so give it a moment to connect.