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Reliance Plumbing Sewer & Drainage, Inc. Blog

What’s the Deal with Slab Leaks?

slab-floor-in-kitchenThey’re bad news—that’s what!

Okay, clearly we need to elaborate on that a bit more. After all, you may not even know what a slab leak is. 

“Slab leak” is a phrase used to describe any leak that occurs in the cold or hot water lines that are set beneath the concrete foundation of your home—the slab. Not only will this type of leak cause significant water waste, but property damage as well. It leads to mildew and mold growth, drywall rot, and more. Plus, a hot water line leak can put extra strain on your tank water heater too, which has to run longer to keep a steady supply of hot water available.

So, what causes these slab leaks? Shouldn’t a pipe beneath your slab be sturdy enough to handle anything? These pipes may certainly seem sturdy, but there are absolutely factors that can lead to leaks. Read on as we uncover a few. 


When too much pressure is placed on the pipes underneath your home’s slab, it can create a leak. This pressure can occur due to a number of reasons, from the shifting of soil causing your home’s foundation to shift as well, to increase water pressure due to another related problem. Pressure-related leaks can create a high risk of damage due to flooding.


Slab leaks tend to be slightly more common with hot water lines than they are cold water lines. This is because pipe corrosion more likely when hot water is involved. The reaction between the material of your pipes and the heat of the water starts corroding it from the inside out. Corrosion can of course happen with cold water lines as well, but this is worth noting.

Aging homes are more likely to have pipe corrosion than a home that’s only a couple decades old. This is because older homes utilized copper or galvanized steel pipes in their foundations. While materials like copper are corrosion-resistant, they’re not corrosion-proof. Electrolysis can still occur, and that’s when corrosion happens.


Have you ever been in a home or building where you could see exposed plumbing pipes? Now, have you ever noticed how sometimes they rattle around as water moves through them? This is because those pipes are contracting and expanding with the temperature fluctuations of cold and hot water.

Plumbing systems today are designed to last, but in an older property, pipes that rattle like this, underneath a concrete slab, will start experiencing abrasion as they rub against the rock surface. Over time, this will lead to leaking.

This is another one of those issues that’s a bit more common in your hot water lines, but still not one to dismiss when it comes to your cold water lines. No matter what the cause, if you suspect a slab leak beneath your property, it’s time to call in a pro. The faster you have your plumbing problem fixed, the less likely of a chance there is for slab leak damage.

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