Cold-water slab leaks
Cold-Water Slab Leak Repair Services in Texas
Last reviewed
A cold-water line leaking under the slab doesn’t warm the floor. It often doesn’t show at all. The first clue is usually a number: the water bill, or the meter dial moving when nothing is on. Call and we’ll connect you with a local Texas crew for cold-water slab leak repair.
Have a recent bill handy; the change in usage helps.
What a cold-water slab leak is
The cold side of your plumbing starts at the main, where water enters the house from the meter, and branches out to every fixture, the water heater supply, toilets, the ice maker and outdoor faucets. In a slab home, part of that network runs beneath the concrete. A leak anywhere along that hidden section is a cold-water slab leak.
Because the main cold line carries water at full supply pressure and feeds everything else, even a small leak on it can lose a surprising amount of water over a month.
Why cold-side leaks are hard to notice
Hot-water leaks announce themselves with warm floors. Cold-water leaks rarely do. Water escaping from a cold line under the slab often soaks down into the soil and sand beneath the concrete instead of rising, especially in the early stages. The signs, when they come, tend to be indirect:
- A water bill that climbs and stays up, with no change in household use.
- A meter leak indicator that moves with every fixture and appliance off.
- The faint sound of running water in a wall or near where the main enters.
- Slightly lower pressure at fixtures.
- Later on, damp flooring, a musty smell or moisture along a baseboard.
Many cold-side leaks are found months after they start, simply because nothing looked wrong.
Tell us how far the dial moved and how long you watched.
Cold-water slab leaks in Texas homes
The same forces that wear hot lines under Texas slabs act on cold lines too. Expansive clay across Dallas-Fort Worth and Central Texas moves the slab and the soil with wet and dry spells; lines rub against concrete and gravel; joints and bends take stress. In homes from the 1960s to the 1980s with copper under the slab, that slow abrasion eventually produces pinholes on both sides of the system.
Where the water is hard, as in much of Central and West Texas, mineral wear inside copper adds to the problem. In Greater Houston, the dense clay and high water table can make it even less likely that a cold-side leak surfaces where you'd see it.
The check you can do
The water-meter check is the best tool a homeowner has for cold-side leaks. Turn off every tap, shower, toilet fill and water-using appliance, including irrigation, softeners and ice makers. Find the meter near the street, note the leak indicator and the main sweep hand, wait five minutes without using water, and look again.
If it moved, water is leaving the system. That doesn't yet mean it's under the slab: a toilet flapper, an irrigation valve, an outdoor spigot or the yard line from the meter to the house can do the same. But it does mean a leak exists.
Ask whether your symptoms point to the cold side.
How a cold-side leak is located
The technician confirms the loss at the meter, then works through the obvious above-ground suspects: toilets, outdoor faucets, irrigation and the water heater's own fittings. Next comes isolation. With the water heater supply shut off, if the meter keeps moving, the leak is on the cold side.
The cold line is then pressure tested. A steady pressure drop confirms the leak is on that line, and the yard line from the meter can be tested separately to make sure the leak is inside the foundation rather than under the lawn.
Locating the exact spot relies more on acoustic listening than on thermal imaging, since a cold leak leaves little heat signature. The technician listens along the line's likely route for the sound of escaping water and may use tracer gas in some cases. The readings narrow the area; the technician should tell you how confident they are.
Local crews know how homes in your area are usually plumbed.
Repair options
The options are the same as for any slab leak: spot repair through the slab, rerouting the cold line above the slab, lining where the line is suitable, or partial or whole-home repiping. Because the main cold line often runs a long way under the slab before branching, rerouting it can mean a new line along an exterior wall or through the attic. The technician will explain the practical route in your house and why one option suits better than another.
After the repair, the line is tested again. If moisture reached floors or walls, restoration companies handle drying and flooring contractors handle replacement.
Ask how the leak will be located first.
Yard line or slab line?
A common question on cold-side leaks is whether the problem is under the house or between the house and the meter. The yard line runs underground from the meter box to where the main enters the foundation. If it leaks, you may see soggy ground, a patch of greener grass, or water in the meter box. If it doesn't show, testing is the way to tell.
The technician can isolate the yard line from the house. If the meter stops moving when the house side is shut off, the leak is in the yard line, which is outside the slab and handled differently. If it keeps moving with only the house side open, the leak is inside.
Cold-water slab leak questions
A warm floor patch or a water heater that runs constantly points to the hot side. If there’s no heat and the main clue is the bill or the meter, the cold side is more likely. A technician confirms it by isolating the water heater supply and watching the meter.
Water escaping from a cold line often drains downward into the soil and sand beneath the slab. It may take a long time, or a lot of water, before moisture works its way up to the floor surface, if it does at all.
It can, especially if the leak is on the main line feeding the house. Low pressure has many other causes, though, so it’s a supporting sign rather than proof.
It could be, but toilets, irrigation and the yard line are common culprits too. Start with the water-meter check. If the meter moves with everything off, call and a technician can work out where the water is going.
Not necessarily. A cold-side leak on the main line can lose a lot of water, and because it’s hidden it can run for months. It’s just less likely to make itself obvious.
Many Dallas-Fort Worth homes from that era do, but earlier repairs and remodels can change what’s actually there. The technician will confirm the material rather than assume.
Usually not as well as it finds hot-water leaks, because there’s little heat difference to see. Acoustic listening and pressure testing do more of the work on the cold side, with tracer gas used in some cases.
A yard line leak is in the underground pipe between the meter and the house. A slab leak is in pipe beneath the house itself. They can produce the same meter movement, and testing separates them.
Bill up, meter moving, nothing visible?
Call and we’ll connect you with a local technician who can find where the water is going.
Same-day visits available in many areas.