Leak detection, before anyone opens a wall

Most leaks are found by their damage, which is the expensive way to find them. Leak detection is the business of finding them by their behaviour instead — before the stain, before the mould, and before anyone opens a wall on a hunch.

The signs that arrive before the stain

A hidden leak announces itself in small ways for weeks or months. The bill goes up without the household changing. A section of floor is warm underfoot in a house with no radiant heat.

Individually each is easy to explain away. Together they are a leak, and the reason to take them seriously is that the cost of a water leak is almost entirely a function of how long it runs.

Smell counts too. A persistent musty note in a basement or a closet, particularly one that is stronger on humid days, is the classic signature of water in a place with no airflow. Trust it before you trust your eyes.

The meter test, which you can run tonight

Before calling anyone, you can establish whether water is leaving your system at all. It takes an hour and it is the single most useful piece of information you can hand a plumber.

That last step is the one people skip, and it is the one that separates a leak under your slab from a leak in the line running under your front yard — two completely different jobs, and knowing which before anyone arrives saves a visit. If it turns out to be the buried side, main water line repair is the page you want.

Where Colorado leaks hide

Housing stock here has its own habits, and leaks follow them. Post-war ranch houses on the Front Range have supply lines run through unheated crawlspaces and slab-built additions bolted onto the back. The 1970s and 80s brought polybutylene, which fails at the fittings and does so quietly. Newer builds have PEX manifolds, which are excellent until a fitting in a wall lets go.

Then there is what the climate does. Expansive bentonite clay soils across much of the metro and the southern Front Range swell and shrink dramatically with moisture, and the movement they impose on a buried or under-slab line is relentless. Freeze-thaw cycling adds a second stress: a Colorado spring can put a pipe through the freeze cycle dozens of times in a season, and each one flexes the joints slightly.

High static pressure does the rest. Water districts on sloped terrain run pressures that are perfectly acceptable at the top of the zone and aggressive at the bottom, and a house at the bottom with a failed regulator is running its fittings well beyond spec every hour of every day. That is why we ask about pressure on almost every leak call — see pressure regulators.

How a leak gets found without demolition

The point of professional detection is that it is non-destructive. Nobody should be opening drywall to look for something. The order of operations is roughly: eliminate the obvious, listen, image, and only then isolate.

Eliminating the obvious means dye-testing every toilet and checking every visible fitting, because a startling proportion of "mystery" leaks are a flapper valve. Acoustic listening comes next — ground microphones and amplified listening discs pick up the specific high-frequency hiss of pressurised water escaping through a small opening, and a skilled operator can follow that sound along a buried line to within a foot or two.

Thermal imaging finds temperature anomalies through finished surfaces, which is why hot-water leaks under slabs are comparatively easy to locate and cold-water leaks are not. Moisture meters, both pin and pinless, map how far water has actually travelled through the material, which is often much further than the visible damage suggests.

Where those do not resolve it, the system gets isolated section by section with pressure tests, or tracer gas is introduced into a drained line and picked up at the surface with a detector.

Under-slab supply leaks specifically

An under-slab supply leak is a failure in a line running beneath a concrete floor, and Colorado's soils make them more common than they should be. The tells are a floor that is warm in one area, hearing water when nothing is on, unexplained damp at the base of a wall, and a bill trending up over several months.

Once located, there are three ways out and they should all be on the table. Spot repair means breaking a small area of concrete, fixing the line and repouring — cheapest, appropriate when the pipe is otherwise sound and the leak is accessible. Full repipe is the answer when the slab lines have already failed more than once, and it is where whole-home repiping comes in.

Be wary of anyone who arrives at one of those three answers before locating the leak precisely. The location determines the economics.

Irrigation, service lines and the green patch

Outdoor leaks in Colorado hide in plain sight for a season at a time, because the water table and the irrigation system give them cover. A cracked lateral on a sprinkler zone waters a patch of lawn beautifully; you notice it only when the rest of the yard goes off in August and one rectangle stays emerald.

The buried service line between the meter and the house is the serious version. Soil movement, corrosion on older galvanised or copper services, and freeze damage at shallow depth all cause it, and the water often surfaces nowhere near the break — it follows the trench, or the utility bedding, or a drain, and appears at the low point.

If the leak is on your side of the meter, it is yours. Most Colorado utilities own to the meter and no further, though a few handle the curb stop, and some offer one-time leak-adjustment credits on the bill if you fix it promptly and document it.

What finding it is worth

Detection has a cost, and the honest way to think about it is as a purchase of certainty. You are paying not to open five walls. On a straightforward interior leak the detection is a small fraction of the repair; on a slab or buried line it is a larger fraction, and it is still cheaper than a wrong guess.

The other side of the ledger is what the leak is costing while it runs. A pinhole passing a small continuous flow moves thousands of gallons a month, and the water bill is the least of it — sustained moisture in a wall cavity or under a slab causes framing damage and mould that is priced in reconstruction, not plumbing.

Ask what the detection fee includes, whether it is credited against the repair, and whether you get a written location with photographs. All three are reasonable requests and most good outfits offer them without being asked.