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How to fix a slab leak

We'll help you recognize a slab leak, shut off water, and know what to expect from a plumber.

How-to · Home plumbing
15 min (shutoff); repair is professional
What you'll need
  • Main shutoff access
  • Plumber with slab-leak experience

At a glance

  • Watch for signs: warm spots on the floor, rising water bills, low water pressure, or the sound of running water when nothing is on.
  • Shut off the main water supply to stop the leak and prevent further damage.
  • A plumber uses electronic leak detection or acoustic equipment to locate the leak under the slab.
  • Repair options include rerouting the pipe above the slab or spot-repair—both require a professional.
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Choose the option that matches what you see. You can jump straight to that section.

Steps

Goal: Recognize a slab leak, shut off water, and get professional repair.

Recognize signs

Goal: Identify that you may have a slab leak.

  • Watch for: warm spots on the floor, unexplained rise in water bills, low water pressure, sound of running water when nothing is on, or cracks in flooring.
  • Good: You notice one or more signs. Proceed to Shut off water.
  • Bad: Unsure—check the water meter with all fixtures off; if it moves, you have a leak somewhere.

Shut off water

Goal: Stop water flow to minimize damage under the slab.

  • Turn off the main shutoff. Confirm that water stops at all fixtures.
  • Good: Water is off. Proceed to Call a plumber.
  • Bad: Water continues or you cannot find the shutoff—call a plumber or utility for help.

Call a plumber

Goal: Have a professional locate and repair the leak.

  • Slab leaks require specialized detection and repair. The plumber will use electronic or acoustic equipment to locate the leak.
  • Repair options: reroute the pipe above the slab or spot-repair by breaking a small section. The plumber will recommend the best approach.
  • Good: The plumber locates and repairs the leak. Proceed to Verification.
  • Bad: Foundation damage is suspected—the plumber may recommend a foundation specialist.

When to get help

Call a plumber as soon as you suspect a slab leak. Do not attempt to locate or repair it yourself. Shut off the main water first. Delaying can worsen foundation damage and mold.

Verification

  • Water is shut off until the repair is complete.
  • The plumber has located and repaired the leak.
  • Water is restored and no new leaks appear.
  • Water bills and floor conditions are normal for several weeks.

Reviewed by Blackbox Atlas

Frequently asked questions

What is a slab leak?
A slab leak is a burst or corroded water pipe under the concrete foundation. Water can pool under the slab, damage the foundation, and cause mold. These leaks require professional detection and repair.
Can I fix a slab leak myself?
No. Locating and repairing a pipe under concrete requires specialized equipment and expertise. You can shut off the water and call a plumber. Do not attempt to break through the slab yourself.
When should I call a plumber for a slab leak?
Call a plumber as soon as you suspect a slab leak—warm floor spots, unexplained water bills, or low pressure. Shut off the main water first. Delaying can worsen foundation damage.

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