How do I know if I have a hidden water leak?

What are the signs of a hidden leak?

Hidden leaks show up in ways that don't look like plumbing at first. Here's what we hear from homeowners before they call.

• A water bill that climbs while your habits stay the same. PWD, BCWSA, and Aqua Pennsylvania all bill on metered use, so a leak shows up as a slow rise.
• Stains, soft spots, or bubbling paint on ceilings and walls, especially below a bathroom or along the path of a pipe.
• A musty, damp, or moldy smell in a room, closet, or basement that has no obvious water.
• Floors that feel warm in one spot, or a tile or vinyl floor that's lifting or cracking, on a slab home.
• The sound of water running or hissing when every fixture is off.
• A water heater or boiler that runs more than usual, because a hot-side leak keeps pulling fresh water in.
• Lower water pressure that started suddenly.
• Wet or unusually green patches in the yard, or a dip forming above the service or sewer line.

How do I run a water meter test?

The meter test tells you whether there's a leak somewhere between the meter and your fixtures. It doesn't tell you where, but it settles the question.

Turn off every fixture and appliance that uses water: faucets, showers, ice maker, washing machine, dishwasher, sprinklers, humidifier. Make sure no toilet is refilling. Then find the meter. In a Philadelphia rowhome, it's usually in the front basement near where the service comes through the wall. In Bucks County it may be in the basement, a crawlspace, or a pit in the yard near the street.

Look for the small leak indicator on the meter face. It's a little triangle, star, or dial that spins when any water moves. If it's turning with everything off, water is going somewhere. If your meter has no indicator, write down the full reading, wait a couple of hours without using water, and read it again.

To split hot from cold, close the cold inlet valve on top of the water heater and repeat. If the meter stops, the leak is on the hot side.

Why do slab homes and radiant floors hide leaks so well?

A slab-on-grade home has no basement or crawlspace. The water supply and, in original Levittown houses, the radiant heating loops are buried in or under the concrete. When a pipe fails there, the water goes into the ground or soaks the slab. You don't see a drip. You feel a warm spot, notice the floor covering lifting, or get a bill that doesn't make sense.

With in-slab radiant heat, the giveaway is often the boiler. It needs makeup water more often, the pressure gauge drops, or one section of floor stays cool while another is oddly warm. A leaking supply line under a slab shows the same warm-spot pattern on the hot side and a cold, damp spot on the cold side.

We find these with pressure testing and, where it helps, listening and thermal tools, then open only the section of slab we need to. On a radiant loop, rerouting the pipe above the slab is sometimes the better option than chasing it under the floor. We'll explain both.

Where do hidden leaks usually start?

In our experience, hidden leaks come from a short list of places. Toilets are first: a flapper that lets water into the bowl silently can run for months. Next are supply fittings under sinks and behind the fridge and washing machine, where a compression nut or a braided hose slowly weeps into the cabinet or the wall.

Then come the pipes inside the walls and floors. Older copper develops pinhole leaks. Galvanized steel rusts through at the threads. Cast-iron and clay drain lines crack and let wastewater into the soil under the house, which shows as a smell or a soft spot rather than a puddle.

Outside the house, the water service from the curb stop to the foundation is a big one in Philadelphia and Ardmore. An old lead or galvanized service can leak for a long time under the sidewalk before it surfaces. If the meter test shows a leak and nothing inside the house is wet, the service line is the next place we look.

How do we find the leak, and what's next?

Finding a hidden leak is detective work, so we start with the same steps you did: a meter test, hot-versus-cold isolation, and a walk through the house looking and listening. From there we use pressure tests on individual runs and inspection tools to pin it down, and a camera inspection if the drain or sewer line is the suspect.

What drives the estimate is where the leak is and what it takes to reach it. A fitting under a sink is a quick repair. A pipe in a finished wall means opening and patching drywall. A slab leak depends on whether we reroute or open the floor. A service line leak depends on the length from the curb, the depth, the sidewalk or driveway on top, and permit requirements from Philadelphia L&I or your township. Our underground crews do that excavation themselves.

If you've run the meter test and it moved, request service and tell us what you found. We'll locate it, show you what we see, and give you options before any work starts.