Slab Leak Signs and How to Confirm One in Denver

Does your home even have a slab?

A slab leak can only happen where water pipe is buried in or under concrete. Plenty of metro Denver houses have full basements with supply lines hung from the open joists, and a leak there is visible and easy to reach. The homes to think about are slab-on-grade ranches and townhomes, additions poured on the ground, garage conversions, and finished lower levels where a builder set pipe into the floor. If you are unsure, follow the main line from where it enters the house. If it disappears into the concrete, part of your plumbing is under the slab.

Which warning signs matter most?

HomeAdvisor's slab leak guide lists the signs plumbers see most often:

• A warm patch of floor. A leak on a hot line heats the concrete above it. Bare feet, a pet that suddenly favors one spot, or tile that feels warmer than the rest are all clues.
• Dampness or standing water where no fixture is nearby, often at a seam in vinyl or along a baseboard.
• Running water sounds when everything is off, most noticeable late at night.
• A sudden change in water pressure at faucets and showers.
• A water bill that climbs while your habits stay the same.

HomeServe adds cracks in plaster or brick and raised spots in the floor, which can show water working on the soil below. A water heater that seems to run constantly is another hint that hot water is escaping somewhere. None of these alone proves a slab leak; a toilet that runs or a weak shower can mimic several of them. Low pressure in particular has many causes, and our guide on why water pressure drops helps rule out the simpler ones.

How can you check at home?

Denver Water's leak page lays out a meter test that takes about half an hour:

1. Turn off every faucet, the ice maker, the dishwasher, the washer and the sprinkler controller.
2. Find the meter and note the position of the sweep hand. Many meters also have a small red triangle or gear that spins with even tiny flows.
3. Wait at least 30 minutes without using any water, then look again. If the hand moved, water is leaving the system.
4. Now close the main shutoff in the house. If the indicator stops, the leak is inside the home. If it keeps moving, the leak is underground between the meter and the shutoff.

Denver Water says toilets are the most common leak culprit, so check them before you assume the worst. If the house checks clean but the yard line fails the test, that is a service line repair, which Denver Water says is the property owner's responsibility from the main all the way into the home.

Hot side or cold side?

If your water heater has a shutoff on its cold inlet, close it during a second meter check. A meter that stops when the heater is isolated points to the hot side, which fits a warm-floor symptom. Write down what you find, along with how fast the indicator moved and when you first noticed the symptoms, since that saves the plumber time and helps narrow which run to test first.

Why do slab pipes fail around Denver?

Age is the biggest factor. About 55.5% of Denver homes were built before 1980, with a median year built of 1975. Lakewood is similar at 55.8% (median 1977), and in Arvada the figure is 52.5% (median 1979). Pipe that has been in place for decades wears at joints and bends, and corrosion can thin it from the inside. Newer suburbs are not immune: Thornton's housing has a median year built of 1997, and a fitting nicked during the pour or pipe rubbing against concrete can leak in a house of any age.

Colorado soil is another factor worth knowing about. The state's Planning for Hazards program calls expansive soils one of the most widespread and costly geologic hazards in Colorado, says about 50 percent of the state's soil has a high or very high potential to shrink and swell, and notes that the swelling can put damaging pressure on foundations and slabs. A slab that moves with wet and dry cycles can, in turn, stress any pipe locked inside it. If you have seen cracked concrete, sticking doors or heaving floors, mention it when you call.

How do plumbers find the exact spot?

Pinpointing is the expensive part to get wrong, because every foot of error means more broken concrete and flooring. A good leak detection appointment usually moves from broad to narrow:

HomeAdvisor puts leak detection at about $280 on average, with most homeowners paying between $150 and $400. HomeServe's 2025 guide lists a slab inspection at $300 to $750.

What are the repair options, and what do they cost?

Once the spot is marked, there are three common paths. The plumber can open the floor at the leak and repair the pipe, which suits a single failure in otherwise healthy line. The run can be abandoned and a new line routed through walls or the attic, which avoids the concrete entirely. Or, when the piping has leaked more than once, the plumber can replace the supply lines in that part of the house through a repiping project.

• HomeAdvisor's 2025 figures put the average slab leak repair at $2,280, with most jobs between $630 and $4,400, and a reroute at $600 to $4,000.
• HomeServe's April 2025 guide puts digging into the slab to replace a section of pipe at $700 to $5,000.

Keep in mind that these cost guides cover the country as a whole, and each one groups jobs a little differently, so treat the ranges as a starting point for comparing written quotes rather than a price list. Floor coverings, how much drying is needed and how far the line has to be rerouted move a Denver bill up or down, and flooring repair is usually a separate trade. For a broader look at pricing, see what plumbing work costs in Denver. You can also read more about the ways slab leaks are fixed on our Denver service page.

How urgent is it?

A slow slab leak is rarely an emergency in the first hour, but it is never something to leave for months. Water under a floor feeds mold, soaks into the soil and keeps running up the bill. The EPA notes that mold will not grow on wet materials dried within 24 to 48 hours, which is a reason to act quickly once flooring is wet. If water is actively pooling or a hot line is pouring into the house, close the main and treat it like a burst pipe; our burst pipe checklist covers the first steps.

After the repair, Denver Water says customers may qualify for a bill adjustment for the leak, so keep the invoice. Buyers and sellers who want to know about old piping before closing can ask for a whole-house plumbing inspection. In the western suburbs you can reach someone for slab leak repair in Lakewood, and to the north, help with finding leaks in Thornton. Homeowners in Arvada and the rest of the metro can call the number on this page as well.