In this article, the world’s greatest water leak detection expert, Sherleak Holmes, discusses how to discover if your pipes are leaking under your floor.

Uh oh. Do you hear a faint drip, drip, drip coming from somewhere under your floors? That’s never a good sign. A leaking pipe can cause serious damage if left unaddressed. But how do you know for sure if you have a leak? And where exactly is it coming from?

Don’t panic. Leaky pipes under the floor are common problems for homeowners. The good news is, there are ways to detect and diagnose the issue before it gets out of hand. Here’s what to look and listen for to determine if you have a leak under your floors, plus tips on getting it fixed fast.

7 Sneaky Signs Your Floor Pipes May Be Leaking

Listen for dripping or running water. The most obvious red flag is hearing water dripping, running or gurgling under the floor. Get quiet and listen closely. Move around to different rooms and locations to pinpoint the source. Drips usually happen in a steady pattern, while running water sounds more constant.

Check your water meter. Turn off all water devices in your home, then go outside to locate your water meter. If the dial is still spinning, bingo – you most likely have a leak somewhere.

Inspect floors and ceilings for stains. Carefully examine your floors, ceilings and baseboards for water stains or moisture damage. Dark spots, water marks, warping, buckling or soft areas indicate a leak. Stains will likely show up somewhere below the source.

Look for mold or mildew. Sniff out and scan for signs of excess moisture that can breed mold. Look in crawlspaces, basements and under sinks. Mold is a definite clue that water is accumulating somewhere it shouldn’t be.

Notice higher than normal water bills. A spike in your water usage points to a potential leak. Compare bills over the last several months to your typical averages. Unexplained increased costs are a red flag.

Check for sinking or settlement. If sections of your floor feel uneven or sloped, this can mean water is eroding and washing away the soil underneath. Low spots signal a problem area to further inspect.

Smell or see sewer leaks. Sewer gas odors or visible sewage pooling around drains or toilets are dead giveaways of a cracked sewer pipe somewhere beneath. Time to call a plumber!

Where to Look for Leaking Pipes

Around toilets, tubs, and showers. Leaks often develop at water supply lines and drainage pipes under sinks, showers, tubs, and toilets that have been loosened with use over time.

Near dishwashers, and washing machines. Under kitchen sinks and laundry hookups are common leak points too. The vibration of the appliance can rub on connections and hoses.

Around the water heater. Check the floor around your hot water heater for wetness. Faulty tanks or loose T&P valve lines are likely culprits.

Near outdoor spigots. Underground leaks can make their way inside through penetrations used for outdoor hose bibs. Feel around foundation walls for moisture.

Under wall voids. If you have plumbing running through walls to feed upper or lower-level fixtures, leaks can drip down inside the wall itself. You’ll need to cut away drywall to investigate.

Inside crawlspaces. Damp crawlspaces lined with pipes provide openings for leaks. Inspect closely for standing water, erosion, and leaks at joints or elbows.

Under slab foundation. With slab foundations, plumbing runs beneath the concrete floor, where leaks can be very tricky to pinpoint. You may need professional equipment.

How to Find the Exact Source of the Pipe Water Leak

Finding the exact location of an underfloor leak can take some real sleuthing. Here are a few methods to help track it down:

  • Use a stethoscope. A mechanic’s stethoscope can help amplify the sound of running water so you can follow it to the source.
  • Turn off sections of water. Systematically shut off water to different branches in your plumbing system. Check if the sound stops to isolate the problem line.
  • Conduct a flood test. Place buckets or pans under suspect leak locations, then run large amounts of water through nearby drains to reveal the leak site.
  • Use a thermal camera. An infrared camera can detect temperature differences and moisture caused by a leak under the floor. Water leak detection service companies like USA Leaks have this high-tech tool.
  • Hire professionals. Water leak detection service companies have expert ears, high-tech equipment, and inspection cameras on long cable snakes to find even the most hidden leaks under concrete and in crawlspaces.

Fixing Leaky Pipes Under the Floor

Once you’ve detected the leak, the next step is stopping the water flow and fixing the damage. Here are some tips:

  • Shut off the main water valve to your home before starting repairs. This prevents leaks from worsening and new ones from springing.
  • If you know the general source of the leak, shut off water valves for that section too. This isolates it from the rest of your plumbing.
  • Remove any water-logged materials like drywall or insulation that may breed mold if left wet.
  • Repair or replace the leaking pipe section. This may require cutting into drywall or the concrete foundation to access it.
  • For slab foundation leaks, you’ll need to trench through the concrete with special equipment to mend or replace pipes.
  • If there is erosion under the pipe, fill it in with compacted soil or gravel to stabilize it before repairing the line.
  • Consider installing a leak detection system that can catch future leaks early before major damage occurs.

For more information, check out our article on slab leak detection and repair.


Dealing with leaky pipes under the house can be a messy headache. However, addressing problems quickly can save you from extensive repairs down the road. At the first sign of a potential leak, inspect closely and start troubleshooting. And for major pipe repairs under the foundation, always call a professional plumber for proper fixing. That drip, drip, drip might be annoying now, but it’s warning you to take action before your floors are left soaked.