How To Detect a Slab Leak: 5 Signs and When To Call a Pro

A slab leak can silently damage your home for weeks, or even months, before you notice anything wrong. Water seeping beneath your concrete foundation erodes soil, weakens structural supports, and creates ideal conditions for mold growth. For Austin-area homeowners, knowing how to detect a slab leak early can save thousands in repair costs and prevent serious water damage.

The challenge is that these leaks hide underground, completely out of sight. You might notice subtle clues like a spike in your water bill or warm spots on your floor, but connecting those dots isn't always straightforward. That's why understanding the warning signs, and knowing when to bring in a professional, matters so much.

At Water Damage Repair Tech, we've helped homeowners throughout Austin, Round Rock, Cedar Park, and surrounding communities address water damage caused by undetected slab leaks. Our IICRC-certified team responds quickly to minimize damage and restore properties to their original condition. In this guide, we'll walk you through five common signs of a slab leak and explain exactly when it's time to call for expert help.

1. Water shows up where it should not

Unexplained water appearing on your floor is one of the most visible signs of a slab leak. You might notice damp spots on tile or carpet, puddles near baseboards, or water seeping through cracks in your concrete. This moisture often appears without any obvious source like a leaky faucet or appliance malfunction.

What this can look like inside the house

You'll typically find wet patches on flooring in rooms like bathrooms, kitchens, or hallways where water lines run beneath the slab. The water may appear as persistent dampness that returns even after you dry it. Sometimes you'll see discoloration on baseboards or carpet edges, or notice that certain areas of your floor feel softer than others. In severe cases, water can actually pool on the surface.

Fast checks to rule out obvious causes

Before assuming you have a slab leak, check all visible plumbing fixtures for drips or leaks. Inspect your toilet base, dishwasher connections, and refrigerator water lines. Look under sinks and around appliances for any signs of moisture. If these checks come up empty and the water keeps appearing in the same spot, you're likely dealing with a problem beneath the foundation.

Learning how to detect a slab leak early helps you avoid extensive structural damage and costly repairs down the road.

Why this points to a slab leak

When water consistently appears in the same location without an identifiable source, a leak under your concrete foundation becomes the likely culprit. The water travels up through tiny cracks in the slab or follows the path of least resistance until it emerges at the surface.

When to call a pro right away

Contact a professional immediately if the water spreads quickly, appears in multiple locations, or if you notice cracks forming in your foundation. Water Damage Repair Tech offers 24/7 emergency response to stop slab leaks before they cause catastrophic damage to your Austin home.

2. Your water bill spikes or the meter keeps moving

A sudden jump in your water bill with no change in your household habits is a strong indicator of a hidden leak. You might see your monthly bill climb by 20, 30, or even 50 percent without any obvious explanation. Even more telling is when your water meter continues to spin even though every faucet, toilet, and appliance is turned off.

What counts as "unexplained" water use

Unexplained water use means your consumption increases significantly without a corresponding change in your daily routine. You're not running sprinklers more often, no one is taking longer showers, and you haven't added any new appliances. The water bill simply climbs month after month. This pattern suggests water is flowing somewhere in your system continuously.

How to do a quick water meter test

Turn off every water-using appliance and fixture in your home, including ice makers and washing machines. Locate your water meter and write down the numbers exactly as they appear. Wait one hour without using any water, then check the meter again. Any movement indicates water is flowing somewhere.

What the results usually mean

If your meter moved during the test, you have a leak somewhere in your system. A small change suggests a slow leak, while significant movement points to a major problem that could be under your slab.

Understanding how to detect a slab leak through meter testing gives you concrete proof that water is escaping your plumbing system.

When to escalate to professional leak detection

Contact Water Damage Repair Tech immediately if your meter test confirms continuous water flow or your bill jumped by more than 15 percent. Our IICRC-certified team uses advanced leak detection equipment to pinpoint slab leaks without unnecessary demolition.

3. You hear running water when nothing is on

The sound of running water echoing through your home when every fixture is turned off is a clear warning sign. You might hear faint rushing sounds beneath your floor, through walls, or in specific rooms. This persistent noise indicates water is flowing somewhere in your plumbing system, and when you can't identify the source, a slab leak becomes a strong possibility.

Where slab leak sounds tend to come from

Slab leak sounds typically originate from areas where water lines run beneath the foundation, such as bathrooms, kitchens, and laundry rooms. The sound often seems to come from directly below the floor or through baseboards. You might notice it's louder in certain spots and quieter in others, helping you identify the general location.

How to listen and narrow down the area

Turn off all appliances and water fixtures in your home to eliminate background noise. Walk slowly through each room and listen carefully at floor level, paying special attention to areas where you've noticed other symptoms. Press your ear against the floor in different locations to determine where the sound is loudest.

Common false alarms to rule out

Check your toilet fill valves to make sure they're not running continuously. Inspect your water heater for sediment buildup that can cause gurgling sounds. Verify that outdoor irrigation systems are completely shut off and no one is using water in a different part of the house.

Knowing how to detect a slab leak through sound helps you identify problems before visible damage occurs.

When sound alone warrants a pro visit

Contact Water Damage Repair Tech immediately if the sound persists after ruling out obvious causes or if you hear it consistently in the same location. Our team responds within 30 minutes to prevent further damage to your Austin-area home.

4. You feel warm spots on the floor

Warm or hot spots on your floor are a telltale sign of a hot water slab leak. When a hot water line breaks beneath your foundation, the heated water seeps upward and warms the concrete above it. You might notice these spots feel oddly warm to bare feet, especially in rooms where hot water lines run like bathrooms, kitchens, or near your water heater.

Why hot water slab leaks create hot spots

Hot water leaking from pipes beneath your slab transfers heat directly through the concrete. The warmth concentrates in specific areas, creating noticeable temperature differences compared to surrounding floor surfaces. This symptom is unique to hot water line leaks and won't appear with cold water slab leaks.

How to confirm it without tearing anything up

Walk barefoot across your floors in suspected leak areas at different times of day. The warm spot should remain consistently warmer than adjacent flooring. Use your hand to feel for temperature differences along baseboards and in corners where hot water lines typically run.

Learning how to detect a slab leak through warm floor spots helps you catch hot water line failures before they waste energy and damage your foundation.

What to watch for with your water heater

Monitor your water heater for signs of overwork like constantly running or unusual cycling. Check if your hot water runs out faster than normal, which could indicate hot water is escaping through a slab leak instead of reaching your fixtures.

When this sign becomes an emergency

Contact Water Damage Repair Tech immediately if the warm spot expands rapidly or your water heater runs continuously. Our certified team provides 24/7 emergency response throughout Austin to stop hot water slab leaks before they cause structural damage.

5. Water pressure drops across the house

A noticeable drop in water pressure affecting multiple fixtures throughout your home can signal a slab leak. Unlike a single fixture with low pressure (which usually indicates a localized problem), whole-house pressure drops suggest water is escaping somewhere in your main supply line. You'll notice weaker flow when showering, filling pots, or running multiple faucets at once.

How a slab leak affects pressure at multiple fixtures

When a pipe beneath your foundation breaks, water leaks out before reaching your fixtures. This reduces the available pressure throughout your entire system. The problem worsens when you use multiple fixtures simultaneously because the leak diverts even more water away from where it should go.

Quick pressure checks you can do at home

Turn on several faucets at once and compare the flow to what you remember as normal. Check your shower pressure during peak usage times. Run your washing machine while someone showers to see if the pressure drop becomes more obvious.

Understanding how to detect a slab leak through pressure changes helps you identify problems that affect your entire plumbing system.

Other causes that mimic this symptom

Pressure regulators can fail, creating similar symptoms without any leak present. Corroded pipes, partially closed main valves, and sediment buildup in your water heater all reduce pressure. Rule these out before assuming you have a slab leak.

When low pressure suggests an under-slab leak

Contact Water Damage Repair Tech if pressure drops suddenly without explanation or gradually worsens over weeks. Our certified team uses specialized equipment to locate slab leaks quickly throughout Austin and surrounding areas.

Next steps

Knowing how to detect a slab leak gives you the power to catch problems before they cause catastrophic damage. The five signs we covered in this guide all point to water escaping beneath your foundation. Each symptom, from unexplained water and spiking bills to phantom sounds, warm floor spots, and pressure drops, demands attention. When you spot multiple signs together, the urgency increases.

Acting quickly when you suspect a slab leak protects your home's structural integrity and prevents mold growth. Waiting only allows water to spread further, eroding soil and weakening your foundation. The longer a leak runs, the more expensive repairs become.

Water Damage Repair Tech provides 24/7 emergency response for Austin-area homeowners facing water damage from slab leaks. Our IICRC-certified team uses advanced detection equipment to locate leaks without unnecessary demolition, and we respond within 30 minutes to minimize damage. Contact us today for a free estimate on water damage repair and restoration services.