Heard a Hiss? It Might Be a Slab Leak. Here's What to Know.

Nothing is worse than lying in bed at night listening to the faint sound of running water. Maybe you’ve even noticed mysterious warm spots on your floor. Both could be a warning sign of a hidden problem with your plumbing system. Slab leaks tend to happen in homes with concrete foundations. When left untreated, these leaks can cause major damage.

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Professional slab leak detection and repairs can prevent flooding and protect your structure from loss. This article covers everything you need to know about slab leak plumbing, including the signs and costs of repairs.

What Is a Slab Leak?

In 2023, approximately 72% of new homes were constructed on concrete slabs. Some of these utilized under-slab plumbing. Under-slab plumbing refers to plumbing installed under these concrete slab foundations. Sometimes, when a house is built, the plumber lays the pipes before the foundation is poured to save time and to use less materials. Additionally, in hot areas, pipes are often laid first and encased in concrete to keep the water coming into the home cooler. Surrounding the pipes with concrete doesn’t affect the functionality, but it can make it very difficult to replace, detect and repair slab leaks, which happen when the pipes crack and begin leaking water.

What Are Some Signs of a Slab Leak?

Because slab leaks occur deep within your foundation and under your home, you may not notice you have a problem until the damage has occurred. However, there are a few telltale signs you have water under your house. If you notice any of the following, you may have a slab leak.

• Warm spots on the floor. Leaking hot water pipes under the slab can cause specific spots on your floor to feel warm.

• Spikes in your water bill. If your water usage hasn’t changed but you’ve noticed a sudden increase in your bill, it could be an indication of a leak in your concrete slab water lines.

• Sounds of running water. If you hear a hissing sound or the noise of running water when everything is off, it might be time to contact a professional plumber for an inspection.

• Damage to flooring. Wood floors can soak up a lot of water before they begin warping and you notice dampness.

• Wet spots on the floor. If you have carpet, you may notice wet spots or areas that are always damp. This dampness can lead to mold and mildew growth and even insect infestations.

• Puddles surrounding your home. Standing water around your home’s foundation is never a good sign. While it can be a sign of clogged gutters or damaged sewer lines, it may also indicate a slab leak.

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How Is a Slab Leak Fixed?

Fixing a slab leak can be tricky and requires an experienced plumber who uses state-of-the-art slab leak detection tools. Once you find the leak, you have four options for repairs:

• Pipe rerouting. With pipe rerouting, a new pipe is placed on top of the ground for water to move through. This method is for short damaged sections.

• Repiping. Repiping works well for multiple foundation leaks. This solution calls for digging up the concrete and cutting through floors. It’s an invasive process that can cause soil shifts.

• Pipe relining. Also referred to as trenchless pipe repairs, pipe relining is often used for minor repairs on copper pipes. A liner is inserted into the damaged pipe and pressed into place. The new liner seals all leaks and prevents new ones from occurring.

• Spot repairs. Spot repairs require opening the slab at the leak site and replacing the damaged section with a new pipe. This method is ideal when the exact site of the leak has been located and isolated.

How Much Does It Cost to Fix a Slab Leak?

The cost to repair a slab leak depends on where the leak is, how it's repaired and the cost of labor where you live. According to HomeGuide, the typical cost to repair a concrete slab leak is between $500 and $3,500 (CAD 721 and CAD 5,044) for pipe relining. Repiping costs between $700 and $5,000 (CAD 1,009 and CAD 7,206), and replacing the slab and your plumbing system can cost up to $10,000 (CAD 14,413) or more.