How To Identify and Fix a Slab Leak

Amy Pawlukiewicz
Written by Amy Pawlukiewicz
Updated September 20, 2021
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If you suspect a slab leak, call in professionals ASAP to prevent further damage

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There are a few problems out there that compete for the title of “Worst Home Problem,” and a slab leak is definitely one of the nominees. But with slab foundations comprising 65% of new homes built in 2020, leaks are still a problem for many homeowners. These leaks can wreak havoc on your home and be very costly, so it’s important to call a contractor immediately if you suspect you have a problem.

Signs You Have a Slab Leak

Unfortunately, visually identifying a slab leak is nearly impossible for homeowners and requires professional intervention. However, there are several signs to pinpoint the problem, including:

  • Increasing water bills

  • A hissing sound or sound of running water under the sink

  • Warm, moist spots on your ground floor

  • Suddenly low or decreasing water pressure

  • Constantly wet ground near your home’s foundation

  • Mold growth

Slab Leak Causes

If you have a home with a concrete foundation, your main water pipes are likely underneath your foundation. Slab leaks occur when a pipe leaks under the foundation, but there are a few leading causes:

  • Pipe corrosion due to an acidity or alkalinity imbalance in your water

  • Normal “wear and tear” as pipes vibrate and rub against the soil, concrete, and other things surrounding them

  • Shifting soil due to the ground expanding and contracting in hot and cold weather

  • Improper pipe construction or installation

This problem is not a DIY project, and you should hire a local foundation contractor to identify exactly what is causing your slab leak and how to fix it.

Ways To Fix a Slab Leak

Repiping or Rerouting

When the leak involves multiple pipes, plumbers usually repipe the home instead of repairing the old pipes. They install a new plumbing system made of either copper, CPVC, or PEX, which are more durable options than those typically used in slab foundations’ original piping. In some cases, the pro will reroute your pipes through your home’s walls and attic instead of under the foundation.

Remember that repiping requires some demolition if pipes inside your walls or under your floors need replacing. The project can take multiple days, and you may need to consider staying somewhere else if the contractors need to jackhammer through your floors. A slab leak reroute usually costs at least $1,500, not including the cost to repair the foundation and walls if the contractor must break through them.

Repairing the Pipes

Repairing the pipes is the least costly option for fixing a slab leak, but only if your contractor knows the leak’s exact origin. Your plumber identifies the leak using trace equipment and infrared thermometers to pinpoint the leak. They then drill a hole in the floor and repair the pipe. However, if they are incorrect and have to drill multiple holes to find the culprit, you could have a pretty big mess on your hands. Pipe repair usually costs between $150 and $300.

Tunneling

Tunneling under the house is an alternative to jackhammering holes in the floor and is a technique used if you don’t want to damage your home’s interior. Your contractor will identify the leak, then dig an access pit next to the closest wall and tunnel underneath your house to repair the leak.

As this process usually requires an entire excavation crew, it is usually the most expensive since you also pay labor costs. However, it is the least invasive option, so if maintaining the integrity of your home’s interior is a priority, tunneling is the best option. The costs can run from as low as $2,500 to more than $20,000 for the most complicated jobs

Pipe Lining

Pipe lining, or epoxy restoration, is accomplished when a plumber finds the hole in a pipe and injects epoxy into the flaw, lining the old pipe and sealing up any leaks and holes. This is a low-cost alternative to other repair methods, but some controversy surrounds this method's efficacy.

Factors That Influence the Cost of Slab Leak Repairs

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The cost of slab leak repairs varies and depends on several factors. The location and accessibility of the leak and the type of repair needed are significant contributors to the cost. Labor costs, like those required for tunneling versus drilling holes, also play a part. And finally, if your concrete slab needs to be replaced or requires heavy repairs after completing the pipe repairs, you can count on another hit to your wallet. 

Be sure to get quotes from multiple professionals and have them outline all the costs before you begin your repairs.

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