How can I tell whether there is a hidden leak at all?

The water meter. Turn off every tap and every appliance that uses water, including the ice maker and any irrigation, then look at the meter. Most have a small dial or a triangle that turns with the slightest flow. If it is moving with nothing on, water is leaving the system somewhere between the meter and the taps. If the house is on a well and has no meter, watch the pressure gauge on the tank instead: with nothing running it should hold steady, and a pump that kicks on by itself is making up for water that is going somewhere.

The stain is on the ceiling but the bathroom above it is bone dry. How is that possible?

Because water travels before it shows. A leak in a water line or a drain fitting can run along the framing above the ceiling, follow a pipe downhill, and come through the ceiling at the first place it can pool, which can be a room away from where it started. The dry bathroom is a clue, not a contradiction: it says the leak is somewhere the water can reach that ceiling from, and that is a shorter list than it sounds.

What is a slab leak, and how is one found without breaking up the floor?

A slab leak is a water or drain line leaking inside or under the concrete floor of a house built on a slab. The signs are a warm patch on the floor, a meter that will not stop, a sound of water with nothing on, or a floor that stays damp. It is found by checking the lines one at a time and then pinpointing the leak with the right equipment, so the floor is opened once, in one place, rather than chased.

Will walls have to be opened to find it?

Usually one, where the leak actually is, and it is opened last rather than first. Everything before that is done from outside the wall: the meter test, checking the lines one at a time, and pinpointing the spot. The point is that the opening made is the smallest one that reaches the leak, because every opening that is not over the leak still has to be closed and painted afterward, and the leak still has to be found.

Water Leak Detection, Slab and Hidden Leaks, Natick MA

Water, not gas. This page is about water appearing where it should not: behind a wall, above a ceiling, under a floor, or under a concrete slab. If you can smell gas, that is gas leak detection, it is a different job, and it comes first.

What it covers

Leaks you cannot see. A supply line inside a wall or under a slab, a waste line weeping into a ceiling, a fitting buried in a floor, a service line under a driveway or a lawn. The work is establishing that there is a leak at all, then finding exactly where the water is coming from, and doing both before anybody starts cutting.

The reason this is its own job is that the wet patch is often not above the leak. Water runs along the framing, follows a pipe downhill, soaks through insulation and appears at the lowest or the weakest point it can reach, which can be a room away and a floor down. The bathroom above the stain is dry because the leak is not in it. Opening the ceiling where the stain is finds a wet ceiling and nothing else.

The hardest version is a house built on a concrete slab, with a pipe leaking inside or under the floor where nobody can see or reach it. That is what this page is for too.

What the job involves

Confirming there is a leak. Taps and appliances off, then the water meter watched. A meter that keeps moving with nothing running means water is escaping somewhere. On a house with a well and no meter, the pressure gauge on the tank tells the same story.
Supply or drain. A leak in the water supply runs all the time and shows on the meter. A leak in a drain only runs when something drains, and is found by running fixtures one at a time. Which one it is changes where to look.
Narrowing it down. Parts of the system checked one at a time, so the search shrinks from a whole house to one stretch of pipe.
Pinpointing. The exact spot located with the right equipment for the job, so the opening that gets made is as small as it can be.
Opening and repairing. Access made where the leak is, the failed section repaired or replaced, and you are told if the rest of that pipe looks like it is heading the same way.
Testing again. The water turned back on and the meter watched again, because finding one leak is not proof there was only one.

When you need it

A water bill that jumped with nothing changed in the household
The meter creeping with every tap and appliance off
A damp or discolored patch on a ceiling, with a dry room above it
A warm spot on a slab floor, or a patch of floor that is never quite dry
A musty smell in one room that does not shift
The sound of running water when nothing is running
Paint blistering, plaster bubbling, or flooring lifting at the edges
Mold returning in the same corner after every cleaning
Water pressure that has quietly dropped through the house
A wet patch in the yard that stays wet in dry weather
A well pump that cycles on and off with no water being used

Why it matters

A hidden leak does its damage at its own pace and out of sight. The water is not the expensive part. The expensive part is what it soaks: framing, subfloor, insulation that stops insulating, and finishes that have to come off to dry anything under them.

Wet cavities also grow things. Mold needs moisture and time, and a slow leak supplies both generously, which turns a plumbing repair into a remediation job the longer it runs.

The argument for detection specifically, rather than opening walls on a hunch, is arithmetic. Locating first means one small opening in the right place. Guessing means several openings in the wrong places, all of which still have to be closed up and made good afterward, and the leak still has to be found.

The age of the house matters. Older houses can still have galvanized steel water pipe that rusts from the inside, and copper can develop pinhole leaks with age. Neither fails all at once, so a leak found in one place is a reason to look at the rest of that pipe.

How Connerney handles it

Licensed and insured. Licensed and insured in Massachusetts.
Located before opened. The smallest access that reaches the fault, rather than a wall opened on a hunch.
Tested before we leave. The water back on, the meter watched again, and the repair confirmed to have actually ended it.
Owner run. Bill Connerney owns the business, answers the phone and books the jobs, and our team of experienced plumbers does the work. Rated 5.0 on Google across 20 reviews, and BBB accredited since 2018.

Questions people ask

How can I tell whether there is a hidden leak at all?: The water meter. Turn off every tap and every appliance that uses water, including the ice maker and any irrigation, then look at the meter. Most have a small dial or a triangle that turns with the slightest flow. If it is moving with nothing on, water is leaving the system somewhere between the meter and the taps. If the house is on a well and has no meter, watch the pressure gauge on the tank instead: with nothing running it should hold steady, and a pump that kicks on by itself is making up for water that is going somewhere.
The stain is on the ceiling but the bathroom above it is bone dry. How is that possible?: Because water travels before it shows. A leak in a water line or a drain fitting can run along the framing above the ceiling, follow a pipe downhill, and come through the ceiling at the first place it can pool, which can be a room away from where it started. The dry bathroom is a clue, not a contradiction: it says the leak is somewhere the water can reach that ceiling from, and that is a shorter list than it sounds.
What is a slab leak, and how is one found without breaking up the floor?: A slab leak is a water or drain line leaking inside or under the concrete floor of a house built on a slab. The signs are a warm patch on the floor, a meter that will not stop, a sound of water with nothing on, or a floor that stays damp. It is found by checking the lines one at a time and then pinpointing the leak with the right equipment, so the floor is opened once, in one place, rather than chased.
Will walls have to be opened to find it?: Usually one, where the leak actually is, and it is opened last rather than first. Everything before that is done from outside the wall: the meter test, checking the lines one at a time, and pinpointing the spot. The point is that the opening made is the smallest one that reaches the leak, because every opening that is not over the leak still has to be closed and painted afterward, and the leak still has to be found.

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Where we work

Based in Natick, working across MetroWest Massachusetts.

Plus the surrounding MetroWest towns. If you are nearby, call and ask.

Leak detection