Field guide
Plumber Slab Leak Pages: The Meter Test Is the Pitch
The warm patch is the tell
A slab leak is a leak in a water supply line running under a concrete slab, and the homeowner cannot see it. What they can see is the evidence it leaves behind. A warm patch on the floor that does not track with sunlight or a heating duct usually points to a hot water line leaking under that section of slab, and it is one of the earliest signs that shows up before flooring or drywall takes visible damage. A cold line leak gives no warm patch at all. It shows up as a bill that climbs with no change in use, pressure that drops at several outlets at once, or the sound of running water with every fixture off.
The distinction matters for the page, because it decides what the homeowner is told to look for. Hot line leaks announce themselves through heat: the floor warms, and the water heater runs more often than usual because it keeps refilling and reheating water that is escaping under the slab. Cold line leaks announce themselves through numbers: the meter moves, the bill rises, the pressure falls. A page that lists both sets of signs, and says which kind of leak each one points to, is a page the homeowner can actually use at midnight. A page that lists generic leak signs is a page they scroll past.
The ten-minute meter test
The fastest check a homeowner can run takes ten minutes and a look at the water meter. Turn off every faucet, shower, dishwasher, washing machine, ice maker, and irrigation controller, and make sure no toilet is refilling. Then find the meter, usually in a concrete box near the curb, and look for the leak indicator, a small triangle, star, or wheel that spins when any water flows. If it is moving with everything off, water is leaving the system somewhere. Write down the reading, wait one to two hours without using any water, and read it again. Any change means a leak.
One more step narrows it down before anyone is called. Close the shutoff valve where the line enters the house and check the meter again. If the meter stops, the leak is inside the house, which includes under the slab. If it keeps moving, the leak is between the meter and the house, often in the yard line. The page should say plainly what the test cannot do: it confirms a leak exists, it does not locate it under the slab. Pinpointing takes a plumber with acoustic listening gear, pressure isolation testing, or thermal imaging for a hot line, and the page that says so is the page that gets the detection call instead of the DIY attempt.
What detection costs, and what it does not include
Detection and repair are billed separately, and the page should say so before the homeowner asks. Detection typically runs $150 to $600. Repair runs from roughly $630 for a spot repair to $15,000 for a full repipe, before any water damage restoration. The leak water itself starts as Category 1 under the IICRC S500 standard, clean supply water, though prolonged contact with soil under the slab can shift that. A page that prints the detection range and names the repair range is answering the only question the homeowner is asking at that point, which is what will this cost me, and it is doing it before the competition does.
Related reading
If this topic is useful, these earlier guides go deeper on connected questions: Plumber Emergency Call Pages: The Bill Has Four Lines, Not One, Plumber Water Softener Pages: The Hardness Number Decides the Size, and Plumber Drain Camera Pages: Sell the Recording, Not the Look.
Frequently asked questions
How do I know if I have a slab leak?
Look for a warm patch on the floor, the sound of running water with everything off, a bill that rises with no change in use, or pressure dropping at several outlets. No single sign proves it, but several together are a strong reason to arrange detection.
What is the water meter test for a slab leak?
Turn off every fixture and water-using appliance, then watch the meter's leak indicator. If it moves with everything off, water is leaving the system. Write down the reading, wait one to two hours, and read it again to confirm.
How much does slab leak detection cost?
Detection typically runs $150 to $600, billed separately from the repair. A spot repair runs from roughly $630, while a full repipe can reach $15,000, before any water damage restoration.
Does a warm floor always mean a slab leak?
No. Rule out sunlight, a heating vent, and radiant floor heating first. A warm patch with no heat source nearby, especially with a rising bill or a moving meter, is the combination that points to a hot water line under the slab.