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How to Trace a Basement Leak

Basement leaks are unpleasant inconveniences many homeowners experience with each rainfall. Most are due to inadequate drainage away from foundation walls, which typically occurs when rainwater runoff from roofs or adjacent lawns and driveways travels toward foundations rather than away from them. Clogged downspouts, lack of guttering, soil erosion, and damaged perimeter, footer or foundation drains are also commonly responsible for basement leaks. Proper knowledge of a leak’s location is essential to determining the cause of the leak. Trace a basement leak before assuming possible damages or proceeding with repairs.

Things You'll Need

  • 12-by-12-inch aluminum foil sheet
  • Duct tape
  • High-pressure spray nozzle
  • Garden hose
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    • 1

      Tape a 12-by-12-inch sheet of aluminum foil to the leaking basement wall using duct tape. Seal along all four edges of the foil with tape. Leave the foil taped to the basement wall for three days to determine whether the basement wall is just experiencing moisture from condensation or actually leaking water from outdoors.

    • 2

      Inspect the outside surface of the foil for moisture, which signifies a high humidity level indoors is causing condensation on the basement walls. If there is no moisture on the foil sheet’s surface, remove the foil and check the wall for moisture. A moist wall behind the foil indicates moisture is leaking into the basement from outdoors.

    • 3

      Continue tracing the basement leak from outdoors on a dry day. Screw a high-pressure spray nozzle onto the tip of a garden hose.

    • 4

      Blast water onto the leaky exterior foundation wall, starting at one end of the leaky wall and working across it. Slowly move along the wall, wetting a 1-foot-wide section of the wall for five minutes before moving on the next 1-foot-wide section. Have someone else stay in the basement while you spray the foundation to alert you when water begins leaking into the basement.

    • 5

      Determine the source of the leak from where the water is pouring into the basement. The area of the basement where the water is pouring in requires attention.