You notice a damp or oddly warm spot on your concrete floor, and you cannot quite explain it. There is no spilled drink, no pet accident, and it keeps coming back in the same area. In the back of your mind, you are wondering if this is the first sign of a hidden leak under your slab and what that might mean for your home and your budget.
For many Memphis homeowners, the most expensive water damage does not start with a burst pipe that floods a room. It usually starts with small, nagging clues that are easy to blame on humidity, recent rain, or an old house settling. The problem is that when those early signs do point to a leak in or under concrete, waiting to act often gives water more time to damage your foundation, flooring, and plumbing.
At Smith's Plumbing, Heating & Air, we have been working in Memphis and the surrounding communities since 2010, led by a Tennessee and Mississippi Master Plumber. We have seen how early concrete leak detection can turn a potential slab disaster into a focused plumbing repair. In this guide, we will walk through the signs we pay attention to in local homes and what you can do when you start to see them.
Call Smith's Plumbing, Heating & Air at (901) 290-1110 or reach out online now for reliable infrared leak detection in Memphis, TN. We are available 24/7!
Why Memphis Homes Are Vulnerable To Concrete & Slab Leaks
Many homes in the Memphis area are built on slab-on-grade foundations. Instead of a crawl space under the house, your plumbing lines often run directly through or under a thick concrete slab that also supports your walls and floors. Even if your home has a crawl space or basement, it is common to see concrete slabs under garages, additions, patios, and porches, with water lines crossing those areas.
When a home is built, plumbers typically run water supply lines and sometimes drain lines under the slab before the concrete is poured. Those pipes are then locked into place by the slab itself. Over time, normal movement in the soil beneath your home, changes in water pressure, and the age or type of pipe can all stress those lines. A tiny crack or pinhole in a pressurized line can let water escape into the soil or directly into the concrete around it.
Concrete looks solid, but it is naturally porous. Water that escapes from a leaking pipe under or inside the slab can soak into the concrete and then work its way to the surface. It may show up as a damp area, a darker patch, or a white chalky residue. In Memphis, where we see clay-rich soils that expand and contract with moisture, that leaking water can also soften or wash away soil under part of the slab. Over time, this can lead to subtle cracking, settling, or even more serious structural problems if the leaks is not found and repaired.
Because our team at Smith's Plumbing, Heating & Air has spent more than 14 years working on residential slab and in-concrete plumbing in this region, we have a good sense of where leaks tend to develop and how they tend to appear at the surface. That local experience helps us read the early signs in context, instead of blaming every damp spot on humidity or every crack on normal settling.
Subtle Moisture Signs On Concrete You Should Not Ignore
One of the earliest and easiest-to-miss signs of a concrete-related leak is a small, damp area that never quite dries out. You might see this on a basement slab, in a laundry room, in a garage, or along a hallway built on a slab. The key clue is consistency. If the same patch of concrete looks damp, or the flooring over it feels soft or cool, even after several dry days, it deserves attention.
Another common sign is a white, chalky film on the surface of the concrete. This is called efflorescence, and it happens when water moves through concrete, dissolves minerals inside it, and then evaporates at the surface. The dissolved minerals are left behind as that white residue. Efflorescence can appear from surface moisture too, but when you see it inside, away from obvious sources of water, it may indicate that water is working its way up from within or below the slab.
Musty odors along baseboards or in certain corners can also hint at hidden moisture near concrete. For example, the bottoms of walls that sit on a damp slab may absorb moisture over time, feeding mold growth inside or behind drywall. You might see slightly stained baseboards, peeling paint at the bottom of a wall, or carpeting that feels slightly damp along the edge. Because Memphis summers are humid, it is easy to chalk these signs up to the weather. However, humidity alone does not usually cause one stubborn damp spot inside while everything else stays dry.
Our technicians often get called to homes where the only early clue was a persistent damp patch or a faint musty smell near a slab-on-grade room. In many cases, careful testing has revealed a slab or nearby plumbing leak that had been slowly feeding moisture into the area. Catching it at that stage can mean the homeowner fixes the pipe and dries the area out before flooring, framing, and furniture suffer larger damage.
Temperature Changes, Cracks & Other Physical Clues In Concrete
Not every sign of a slab leak shows up as moisture. Temperature differences underfoot can also tell a story, especially when hot water lines are involved. If you notice a particular spot on your tile, laminate, or concrete floor that consistently feels warmer than the surrounding areas, and that warmth has nothing to do with sunlight or heating vents, it may indicate a hot water line leaking under the slab at that location.
Here is what usually happens. Hot water under pressure escapes from a small opening in a line and then spreads into the soil or concrete around it. That water carries heat with it, which warms the concrete in that specific area. The warmth can then be felt through hard flooring and sometimes even through carpet. Because concrete holds heat for a while, that spot may feel warm at times when no hot water is actively being used.
Cracks in concrete are another potential clue, though they can be tricky to interpret. Hairline cracks are common as concrete cures and as a house goes through normal seasonal movement. The cracks that concern us more are ones that appear suddenly, begin to widen, or coincide with other changes like doors starting to stick, floors feeling slightly uneven, or gaps opening along baseboards. When water has been softening or washing away soil under one corner of a slab, that area can slowly drop, creating stress cracks and subtle shifts inside the home.
By looking at the pattern of cracks and movement together with where plumbing lines run, we can better judge whether a leak may be contributing. As a master-led plumbing team, we do not look at cracks in isolation. We consider where bathrooms, kitchens, and utility rooms sit on the slab, how water lines were likely routed, and whether the physical changes in the concrete line up with potential leak paths. That helps us decide where to focus testing instead of guessing and opening concrete at random.
Water Bills, Meter Checks & Plumbing Clues You Can Track
While surface signs give useful hints, your water usage can offer some of the strongest early evidence of a hidden leak. A leak in or under concrete is usually tied to a pressurized water line. That line is constantly supplied with water, whether you are using fixtures or not. Even a modest pinhole can waste a significant amount of water over a month, which often shows up as an unexplained increase on your utility bill.
One simple step is to compare your most recent water bills to previous months and even to the same period last year if you have that information. Look for a steady trend upward that does not match changes in your household, such as new occupants or irrigation changes. If your usage has jumped and stayed high without a clear explanation, it is worth considering that water might be escaping somewhere you cannot see yet.
You can also perform a basic water meter check. Turn off all faucets, fixtures, and water-using appliances in the home, and make sure no one uses water during the test. Then locate your water meter and note the position of the dial or digital reading. Wait about 15 to 30 minutes without using any water, then check the meter again. If the meter has moved noticeably, and you are certain nothing inside or outside is running, it suggests that water is flowing somewhere in the system, possibly due to a hidden leak.
Other plumbing clues can support what you see at the meter. Sometimes you might hear the faint sound of water running when everything should be off or notice that your water heater runs more often than expected. On some systems, you might experience occasional air in the lines or slight pressure changes as the system tries to keep up with a constant leak. At Smith's Plumbing, Heating & Air, we often walk homeowners through these simple checks on the phone or during our initial visit, so we can gather as much information as possible before we move to more advanced testing.
Simple Tests & Observations Versus What To Leave To A Plumber
There are several low-risk, non-destructive steps you can take to keep an eye on suspicious areas around concrete. For cracks, you can mark the ends lightly with a pencil and jot down the date, then check every few weeks to see if they are lengthening or widening. For damp spots, you can take photos and note when they appear. Pay attention to whether they show up after every shower in a nearby bathroom, after rain, or even on completely dry days.
A simple way to tell whether moisture is coming from above or below the concrete is to tape a piece of clear plastic or a freezer bag tightly over a small area of the slab. Leave it in place for a day or two. If moisture appears on the underside of the plastic, closest to the concrete, it suggests moisture is moving up from the slab. If moisture only appears on the top surface, it is more likely coming from the room air or from above. This test is not perfect, but it can help you gather more clues before you call.
What you want to avoid is guessing at pipe locations and beginning to break up concrete on your own. Without a clear plan, it is easy to open the wrong area, increase costs, and still not reach the actual leak. It can also be risky to try to isolate parts of the plumbing system without the right valves or knowledge, since you could create other leaks or pressure issues. Once you suspect a slab or concrete-related leak based on recurring signs and your meter check, it is time to involve a plumber who has the tools and experience to pinpoint it more precisely.
Professional leak detection usually involves a combination of listening equipment, pressure testing, and knowledge of typical pipe layouts in homes like yours. Our technicians at Smith's Plumbing, Heating & Air arrive in fully stocked vans so they can move from basic checks to more targeted diagnostics without multiple trips. In many cases, we can narrow the leak zone to a specific area, which helps keep any necessary concrete opening as small and controlled as possible.
Why Early Concrete Leak Detection Saves Memphis Homeowners Money
It can be tempting to watch a small damp patch or hairline crack for months and hope it goes away on its own. The trouble is that leaks under or in concrete rarely fix themselves. Even a slow leak can steadily add water to the soil or slab, softening support under your foundation, feeding mold growth, and damaging flooring glued or nailed to the concrete. By the time puddles or severe cracking appear, the repair scope often expands well beyond one plumbing fix.
When a leak is identified early, repairs can often focus on a limited section of pipe. That might mean opening a small area of slab or rerouting a single line. When a leak has been active for a long time, you may be looking at multiple rooms of flooring replacement, damaged baseboards and drywall, mold cleanup, and in some cases, structural reinforcement. While every home is different, our experience tells us that early action almost always reduces the amount of demolition and rebuilding needed later.
There is also the ongoing cost of wasted water and extra wear on your water heater if a hot line is leaking. Those monthly costs rarely show up all at once, but they add up over time. Fixing a leak stops that hidden drain on your budget. For families who are worried about the cost of larger plumbing projects, Smith's Plumbing, Heating & Air offers upfront pricing and financing options, so you can see your choices clearly and decide how best to move forward instead of delaying until the damage is worse.
When To Call Smith’s Plumbing For Concrete Leak Detection In Memphis
No single sign guarantees a concrete or slab leak, but certain patterns should prompt a call. If you see a recurring damp or warm spot on a floor over concrete and your water bill has climbed without explanation, it is time to have your system checked. The same goes for a combination of musty odors along walls, new or changing cracks in a slab-on-grade home, and a water meter that moves even when everything is off.
For sudden issues, such as standing water near a slab wall, rapidly spreading cracks, or a dramatic spike in your water bill, you do not have to wait. Our team is available 24/7 to respond to urgent plumbing problems so you can limit damage as much as possible. As a family-owned company with a 5-star rating, over 3,000 reviews, and an A+ rating with the BBB, we take the trust of Memphis homeowners seriously every time we step into a home.