Slab Leak Detection and Repair

In this blog article, concrete slab leak detection expert, Sherleak Holmes, explains how to find and repair slab leaks.

Before we get into this article, Sherleak Holmes wants you to know that slab leak detection and repair can be complicated and it is not a job for your average DIY person. Making mistakes can be very costly and cost far more to repair than if you had just hired a professional slab leak detection expert from the start. So, while you will learn how to find and repair slab leaks, doing it yourself is not recommended. Instead, you should hire a professional slab leak detection service company like USA Leaks.

Finding and Fixing Water Leaks Under Concrete Slabs

Have you been noticing a wet spot, or spots, on your floor, especially when it rains? Has your water bill increased? These are signs that you may have a slab leak. Locating the actual source of the slab leak can be difficult, and that is why calling a slab leak detection expert is recommended.

However, if you want to try and find the leak yourself, with some clever detective work and the right tools, you can track down even hairline cracks in buried pipes. In this article, we’ll walk through the step-by-step process for detecting water leaks under concrete slabs.

Watch for Signs of a Leak

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The first indication that you may have an underground water leak is when you notice wet spots or pooling water on top of the concrete, especially after it rains. This is because water will follow the path of least resistance, traveling along cracks and pipes underneath until it has somewhere to pool above.

Pay close attention to areas where the flooring changes from concrete to wood or carpeting, as leaks often occur at transition points. A musty smell or increase in humidity inside can also be signs of an unseen water leak.

Isolate the Source

Before breaking into the concrete, it’s important to narrow down the location. Turn off individual water sources, like irrigation systems or appliance water lines, and see if the pooling stops. This can help determine if the leak is in the main home supply line or a smaller branch. Also listen closely in different areas with a stethoscope or acoustic listening device to try to hear the sound of running water underground. Areas that are moist to the touch likely indicate you are close to the leak.

Use Moisture-Detecting Tools

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Specialized tools can also help detect excess moisture under the slab so you don’t have to break into the concrete blindly. Moisture meters can be used directly on the concrete surface to find damp areas. Floor leak detector dyes can be fed into the plumbing system, then trace dye patterns will show up at leak sites. Infrared thermal imaging cameras can reveal temperature differences between damp areas and dry concrete. And ultrasound listening devices can pick up inaudible high-frequency noise of pressurized leakage. Combining a few moisture detection methods will help you zero in on the leak before moving to the excavation phase.

Carefully Cut into the Concrete

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Once the general leak location is identified, you’ll need to break into the concrete slab to access the water line. This is a job for a heavy duty concrete saw fitted with a diamond blade. Safety gear like eye protection, gloves, a mask and ear plugs are a must. Carefully score the outline of the section you want to remove, then make relief cuts inside the outline (similar to cutting a square hole in drywall). Go slowly and steadily to control the saw in a straight line, and stop to reposition as needed. Use a chisel and hammer to knock out the cut section of concrete. Keep the hole as small as possible while still allowing room to work.

Inspect Exposed Pipes and Fittings

With the leak site exposed, examine the pipes and connections closely for any sign of cracks, corrosion, loose fittings or punctures. Leaks most often occur at joints in the pipe where fittings connect or pipe materials transition. Flexible water supply tubes are prone to cracks over time. Even the smallest hole or loose fitting can allow pressurized water to escape. Turn the water back on temporarily so you can detect exactly where the water is coming from while the pipes are still visible.

Make Necessary Repairs

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Before repairs, turn off the main water supply to the home. For small cracks and pinhole leaks in otherwise sturdy piping, apply an epoxy sealant thoroughly over the problem area, allowing time to cure completely. Leaking fittings can often be tightened with some pipe sealant/tape and an adjustable wrench.

More serious leaks or bursts require replacing sections of broken pipes with new piping of the same size and material using couplers. Always follow the manufacturer’s instructions for pipe repairs. If the leak is coming from a flexible supply line, just replace the entire tube following shut-off valve installation instructions.

Restore the Concrete

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Once all repairs are made and the pipes have been leak-tested, it’s time to restore the concrete. Remove any remaining loose chips and debris and vacuum the hole to create a clean surface for patching. Use a concrete patching compound, making sure to follow drying time instructions.

For larger holes, it may be easier to purchase a quick-setting concrete mix. Start filling from the bottom up in layers, tamping each layer down. Cover the final layer with a plywood board so the pressure keeps it flat as it dries. Cured concrete patches can be smoothed and sealed over time as needed to match the surrounding slab. With the leak fixed and the concrete restored, you can rest easy knowing all your hard sleuthing paid off!


In summary, detecting and repairing water leaks under concrete takes patience and the right set of tools for each step – like isolating valves, moisture meters, concrete saws, and epoxy sealants. But with a careful inspection, safe excavation, and proper pipe repairs, you can solve the mystery leak before it causes any more costly water damage.

With the right knowledge and equipment, you can feel empowered to tackle this project yourself rather than turning to expensive contractors. Just be sure to always take appropriate safety precautions when taking on major home repairs.

Or, you may find that all of this is far easier by just calling a professional slab leak detection company like USA Leaks.