How do I know if there is water under my floor?

Author: Christy Smitham  |  Last update: Tuesday, July 15, 2025

If you're wondering how to detect a water leak under concrete like a professional, start by following your nose. Water damage quickly causes mold and mildew, which have distinct odors. If you notice a musty or unpleasant odor around, the water lines under the concrete floor could be in urgent need of repair.

How to tell if water is under the floor?

If you see water coming up through the seams, or hear a squishing sound, you can know for sure that water is underneath your floor and it needs to be removed.

How to detect a water leak under the floor?

Buckled, warped, or separated floorboards. A moldy or unpleasant smell. Damp or soaked carpet. Increased water bill.

Why is my floor wet but no leak?

If a plumber can't find any leaks but your floor is still wet, other reasons could exist. It might be because of condensation, especially in humid places or near cold water pipes. Another reason could be a clogged drain, which can build up water on the floor.

How do I find water pipes under my floor?

Today, the best tool for the job is ground penetrating radar (GPR) as it accurately maps metal and PVC pipes. Traditional pipe locators use electricity and magnets to locate underground pipes.

How to Tell if There Is a Water Leak Under Vinyl Flooring?

Do water pipes go under floor?

The pipes that power faucets, showers, toilets, and other fixtures are typically hidden behind walls or under floors, a setup that requires careful planning for proper installation.

How to locate underground water?

Existing hand-dug wells will reveal groundwater depth and give insight into subsurface soil properties. Sand or gravel areas in the bottom of valleys will often be home to groundwater. These layers can be covered by clay or silt, so it's prudent to check these areas thoroughly.

How do you fix water under the floor?

Key Takeaways. If you have water under your floorboards, remove floor coverings and dispose of damaged paper products, dry the area, clean and disinfect the soaked floorboards, ventilate the room, and contact a professional like ServiceMaster of Lake Shore for complete restoration services.

How do I know if my pipe is leaking under the floor?

Warped floors, peeling wallpaper, and water spots on the ceiling are signs that you have a leaky pipe somewhere. Unexpected wet carpets or pools of water on your floor are big signs there is a leak under your floor.

How much does it cost to fix a slab leak?

The average cost of slab leak repair is $2,300. * Depending on the extent of the problem, repairs may cost as little as $630 or as much as $4,400 or more. The location of the leak is the most relevant factor to cost because this determines how difficult it is to access and repair the leak.

What is the easiest way to find an underground water leak?

The easiest way to identify an underground leak is by checking your water meter. If your water meter is moving faster than usual, it's possible you have a leak somewhere in your home. To check this, go outside and look at your water meter.

Why would water be coming up from under the floor?

1) Cracks in the foundation allow water to seep through the floor. This is particularly common in homes with concrete foundations, as concrete is prone to cracks over time. 2) Plumbing leaks in the subsurface cause water to rise and seep through the flooring.

What are signs of water leak under slab?

Signs You Have a Slab Leak
  • Sudden spikes in your water bill.
  • The sound of running water when pipes aren't in use.
  • Moisture or mildew under carpeting.
  • A moving water meter dial when pipes aren't in use.
  • Standing water around the perimeter of your house.
  • Unusually low water pressure.
  • Cracks in your baseboard or walls.

How to detect water leakage under floor?

  1. Watch For Sudden Water Bill Increases. ...
  2. Inspect For Wet or Damaged Flooring. ...
  3. Follow Moldy or Musty Smells To The Source. ...
  4. Take Visible Mold Seriously. ...
  5. Monitor Unusual Noises. ...
  6. Check for Damaged Concrete. ...
  7. Link Potential Outdoor Issues. ...
  8. Know What to Do After Detecting a Water Leak Under Your Concrete Floor.

Will water under floor dry?

You won't be able to dry water that has seeped into and underneath the floors, but you should immediately start drying the visible water on your floors. Mopping and toweling may be sufficient, but if flooding is severe, you may need to use a water pump.

How do you check for moisture under flooring?

Moisture testing before installation of a floor covering

These tests can be carried out with Tramex concrete moisture meters, RH probes, moisture content probes and surface thermometers. These are available in specifically designed concrete moisture test kits.

How do I know if my pipes burst under the floor?

Unexplained Water Pools and Dampness

One of the most obvious signs of a burst pipe is the presence of water where it shouldn't be. If you notice puddles forming under sinks, near water pipes, or along walls, it's likely a sign of a leaking or burst pipe. Water stains on ceilings and walls are also telltale signs.

How to fix a leak under the floor?

Depending on the source of the leak, you may need to break up your concrete floor to access the damaged pipe or repair the leak from above. Fixing a water leak under your concrete floor can be a complex and time-consuming process, so it's best to leave it to a professional.

Why is there water under my floor but no leak?

If it's not the pipes or the foundation, the water might be coming in through your home's windows and doors. Improperly sealed windows can leak on a rainy day, and the water can drain down the wall and into the floors and subfloors. If this happens, you need to start by sealing the windows with caulk.

How do I know if I have water damage under my floor?

How to Spot Water Damage in Your Floors
  1. Discoloration. One of the earliest signs of water damage is discoloration. ...
  2. Warping or Buckling. ...
  3. Soft Spots or Weak Areas. ...
  4. Musty Odors. ...
  5. Peeling, Cracking, or Lifting. ...
  6. High Humidity Levels. ...
  7. Heavy Rainfall and Flooding Risks. ...
  8. Clay-Heavy Soil.

How do I find water under my floor?

Here are some of the signs you should look out for:
  1. Sudden increase in water usage and costs. ...
  2. Cracked areas or bulges of pavement. ...
  3. Unpleasant smells. ...
  4. Low pressure in the water supply. ...
  5. Dirty water. ...
  6. Sounds from pipes. ...
  7. Thermal imaging. ...
  8. Acoustic leak detection.

Can I use my phone to detect underground water?

-Underground water detector mobile app is an easy water leak detector and easy Scan Water Leak Detector A simple water finder This apps transforms any Android into a genuine water identifier to discover water around you, just hold level and follow the needle & This water detection sensor gives you a comprehensive ...

Can underground water be detected?

4.3 Ground-penetrating radar antenna system

FMCW GPR system is used for the detection of underground water in the frequency range from 50 to 150 MHz.

Where does water go when it goes underground?

Underground, water doesn't move much, but rather acts like a sponge, taking up spaces in between cracks in rocks and breaks in the soil. Water that moves into a natural storage area (called an aquifer) beneath the surface of the earth is referred to as groundwater.

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