Slab Leaks – Detection and Repair

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What is a Slab Leak?

When your home was built, the builders installed water lines and sewer lines from the street to your house, running underneath and through the foundation of your home. A house foundation is often referred to as a “slab” since it’s made up of thick concrete and reinforced rebar material.

Other homes may have been built on a “pier and beam” structure which provides easy access to space under the floor. Leaks in these types of home foundations are a lot easier to fix since they are easier to access. In addition, pier and beam type of foundations are gentler on the supply and sewer lines since there is no concrete slab restricting movement of the water pipes.

The soil in Plano and the north Texas area in general is very high in clay content. Clay will absorb water, expand and then push on the slab above. If the soil becomes very dry, which happens quite often in our Texas summers, then the clay can lose moisture and shrink. When the clay shrinks, less support is provided to the house foundation and the weight of the house can cause downward movement.

Slab movement can cause movement in the pipes, weakening the pipe integrity over time. Sometimes the concrete is poured close enough to the pipes in the ground that a small movement in the slab is enough for a rough surface to put pressure on a pipe.

Due to the pressure of the water, a weakened pipe is prone to leak at the weakest spot.

A slab leak happens when water is leaking from a pipe underneath the foundation and makes its way up through microscopic cracks in the slab. Water will make its way through the path of least resistance. Up, down or sideways.

A leak in your foundation can come from one of three types of plumbing lines:

  • The cold water supply lines that come in from the street (from the city water utilities)
  • From your hot water heater. If your hot water heater is in the garage, chances are that the hot water supply lines are run under the slab rather than through the attic.
  • The sewer or drain lines. Waste from the kitchen, bathrooms and washing machines is expelled through the sewer lines back out to the street for processing by the city.

How do I know if I have a slab leak?

A slab leak is an indication that a water or sewer pipe has broken under your home’s foundation. It might have been leaking for a while before making it into your home.

Quite often, you’ll notice one of the following:

  • Warm spots on the floor if there is a leak in the hot water supply line.
  • Damp areas on carpet / flooring
  • A moldy smell in a damp area that has gone unnoticed.
  • The sound of water running through pipes when all faucets and toilets should be off.
  • The water meter spinning around when water shouldn’t be running.
  • An increase in your water bill may be an indication, but make sure you account for any other factors like sprinkler usage. Tip: in the event you have a leak in your sprinkler system, shut off the sprinkler water supply at the street side valve box. It’s a lot easier and less expensive to repair a broken sprinkler line than a leaky foundation slab.
  • Cracks in the wall or flooring. This is common in many houses due to the foundation settling and may not be as a result of a slab leak. The best check is to see if your water meter is running when nothing should be using water in your house.

You should walk around and inspect the perimeter of your home, looking for any unusual wet areas.

If you see the water meter moving, it does not necessarily mean there is a slab leak. It may be also be caused by a running toilet, a dripping faucet, a dishwasher leak or a leak in a pipe in the walls or attic. To be on the safe side, call Staggs Plumbing and we’ll come out and make an accurate diagnosis.

On most water meters, there is usually a leak indicator triangle or some other device that can detect very small leaks, like a leaky faucet or a leak in other places such as a pipe underneath your home’s slab.

In this image, the leak indicator is a red triangle. Even with a small drip from a faucet, you should be able to see a slight movement in this indicator.

If you do see this indicator moving, check all of the faucets inside and outside your home for any drips, as well as toilets that may be leaking water into the bowl. If you are unable to locate the source of the water leak, then you should call out an experienced plumber that is experienced in locating and fixing water leaks.

Can a Slab Leak be Ignored?

If gone unchecked for a long period of time, leaks under the foundation of your home will cause significant structural damage, affecting the value of your home and potentially exposing your family to health risks from mold.

The longer the delay, the higher the eventual cost and inconvenience to fix. Many of our customers are shocked just how much damage was caused by one small leak.

The short answer, obviously, is to have it fixed ASAP by calling the expert plumbers at Staggs Plumbing.

Locating and Fixing a Slab Leak

How do you find out where the leak is coming from?

Specialized listening devices are used to locate the break in the water supply lines. Usually the water supply to the house is turned off and the plumber will pump air into the lines to force out the water from the lines through some of the faucets. Once water has been removed from the supply lines, the air will escape from the crack in the water line. Using the listening device, (much like a doctor would use a stethoscope) the plumber will listen for the sound of escaping air, eventually zeroing in on the exact area of the leak or leaks.

It is important to use a plumbing company that is experienced in locating a leaky water pipe under the slab. If they are unable to accurately detect the source of the leak, then more foundation will need to be either excavated or a larger area of slab needs to be dug up.

Staggs Plumbing has been repairing slab leaks since 1990 and has received numerous consumer awards for their expert work. When you want the job done right, and done right the first time, you’ll realize that this is not a job for amateurs or part-time plumbing companies.

Fixing a Slab Leak

Once the source of the leak has been located, there are normally two options to access the broken pipe.


This method requires digging a tunnel under your house large enough for the plumber to crawl through and access the broken pipe(s). It reduces or avoids the risk of a creating a mess inside your home. The plumbing company will normally find the closet outside wall to the source of the leak and tunnel directly to the source of the leak. Tunneling is a very labor intensive process and can take several hours to complete depending on the distance.

Once the tunnel has reached the leaking pipe, it is normally a quick process to repair or replace the offending water pipe.

Here’s what’s involved when tunneling under a house. This short video shows a relatively easy access to a leak from the pipes under a laundry room of a slab leak repair in Plano.

We chose to dig under the slab from outside because of the close proximity of the water pipes to the side of the house.

When we uncovered the existing water pipes, we noticed that the pipes had come apart, likely due to poor workmanship when the house was built. We repaired the pipes with a more sturdy solution that will probably outlast the house!

Dig up the Concrete Slab

This method involves jack hammering through the concrete of your home’s foundation. Since the concrete can be several inches thick, it requires a commercial grade jack hammer to break through the material.

The concrete slab is usually between 8 and 15 inches thick, and might take a couple of hours to remove enough material to expose the leaking pipe.

Repairing the Water Line

Water supply lines and sewer lines can be made of different materials: PVC, copper or even iron in some older homes.  If there is significant corrosion in the copper or iron pipes, Staggs Plumbing will replace sections of pipes to avoid any further degradation.

Repairing a simple break in the water line is usually a straightforward process, and involves cutting out the damaged section of pipe and replacing it with a new piece. If copper is being replaced, it will be “sweated” on with a torch and solder. PVC pipe fixes will need to use the appropriate type of PVC glue used for high pressure water lines.

Cost to fix a slab leak

The majority of the time is spent detecting the exact leak location and then excavating to expose the actual broken pipe. Tunneling is a very time intensive task as you can imagine, whereas jackhammering through the concrete slab is quicker but creates disruption inside your home with noise and some dust (we try to limit the amount of dust created, although it’s almost impossible to be 100% dust-free)

Will insurance pay for a slab leak repair?

Quite often, your slab leak repair will be covered by your homeowner’s insurance policy, and you’ll only be responsible for the deductible plus an amount to actually fix the broken pipe. Check your insurance policy or ask your insurance agent for clarification. The majority of the cost is taken up by the detection and excavation work. The actual fix is usually a few hundred dollars.

How to Choose the Right Plumber for your Slab Leak

  • Ask for referrals from previous customers.
  • Ask them how long they have been fixing a slab leaks and what do they do to minimize damage and mess inside your home.
  • Do they have an A+ rating from the Better Business Bureau?
  • Are they a master plumber (vs. a tradesman plumber)? A master plumber has advanced education and experience that can make the difference in a job being done right the first time or further problems over time because of poor workmanship.

Staggs Plumbing has built their reputation up via word of mouth and we constantly receive new work from referrals, which is one of the biggest compliments we can get.

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