Do You Have Under Slab Fresh Water Leaks?

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If you’ve noticed higher than normal water bills or your water pressure is suddenly not what it use it be, you might have a fresh water leak.

Your fresh water line runs on a pressurized system and is constantly pumping water from the city’s water lines—meaning there is always water running through your fresh water pipes. This is different from a sewer system which only has water in it when you are running water in the house.

Because there is always water in fresh water pipes, if you do have a leak, it’s like leaving the water running all day, every day.

Signs of a Fresh Water Leak

In addition to high water bills and/or a change in water pressure, you might have one or more of the following signs of a fresh water leak:

  • Higher electric or gas bills
  • Little or no hot water
  • Constant sound of running water
  • Wet spot on floor
  • Standing water in yard
  • Warm/hot spots on floor

Read more about these signs and symptoms here to rule out other plumbing problems.

Causes of Fresh Water Leaks

From what we’ve seen, the number one cause of a fresh water leak is electrolysis—an extremely tiny electric current that forms between two dissimilar metals when there is a fluid flowing across them. While this isn’t the case with newly built homes, older homes’ electrical systems were grounded to their copper water pipes which could cause electrolysis.

Another reason for this electric current is the minerals in our water supply. If a metal-like mineral sticks to a spot on the pipe, this with the water flowing through the pipes could cause the current.

Other possible causes could include:

  • Slight ding or dent in the pipe during installation
  • Possibly defective pipe
  • Ground movement – If the pipe was improperly installed with fittings under the slab, ground movement could cause a leak at the fitting. There should be no fittings on fresh water pipes under the slab
  • Rare for the DFW area – freezing (in the case of above slab pipe)
  • Rusted nail or screw hammered or drilled into the pipe (also above slab)

Many new homes are built with the fresh water lines in the walls and attic but for this post, we are talking about under slab fresh water pipes.

And there are three steps to handling these under slab leaks:

  1. Leak detection
  2. Leak location
  3. Leak repair

Fresh Water Leak Detection

Fresh water leak detection, or determining if you have a fresh water leak, is a much less involved process than it is for an under slab sewer leak.

There are two methods we use to determine if you have a fresh water leak.

One is to look at the city water meter. On the meter there is a triangle, or drip indicator, that will be moving if you have a leak. It also moves if you have the water running in the house. So it’s important to make sure nobody is running water in the house before checking the meter.

The second way is with a pressure gauge. We attach a pressure gauge to a hose bibb on your house, and turn the bibb on. With the pressure gauge attached and hose bibb turned on, we turn off the main water supply so there is no water running to your house from the city.

If the pressure gauge needle doesn’t move, there is no leak. But if it does indicating a drop in water pressure, this means water is escaping from somewhere in the system, and you have a fresh water leak.

Check out this video from our YouTube channel to see what these two different testing methods look like:

Fresh Water Leak Location

Once we’ve determined you have a leak, we need to know where it is. For this we use the best fresh water leak location company in the Dallas area. Find out more about this company and why we consider them a part of the In-House team in this post.

First, they use a pipe locating device to find the lines in your house under the slab.

Then air is pumped into the lines and a special listening device is used to locate the leak. The tech is listening for the sound of the water or air escaping from the lines.

Here’s another video where you can see a live demonstration of this:

Fresh Water Leak Repair

There are a number of ways to repair a fresh water leak under the slab. For an under slab fresh water leak, many companies suggest tunneling from the outside. We do not recommend tunneling for a fresh water leak for a couple of reasons.

Saturated Soil – As we mentioned above, because a fresh water system always has water pumping through it, a leak is like leaving the water running constantly. And in most cases, people don’t realize they even have a leak for at least a couple weeks. Usually, though, it’s a couple of months before the homeowner knows there is a leak.

Because of this, the soil around that leak is completely saturated and like mush. This makes it impossible to make “walls” in the tunnel. So it’s possible the tunnel will collapse into itself making it unsafe for anyone to crawl into and work in the tunnel.

Potential Structural Issues – Because the soil is unstable, there could be problems when digging the tunnel and also when backfilling the tunnel.

This instability could cause structural problems in your home in the future.

What We Recommend

There are a few options available to repair a fresh water leak.

Spot Repair

Our first recommendation in most cases is for us to go through the slab at the location of the leak for a spot repair. Other plumbing companies might try and scare you with horror stories about damaging your home’s foundation or the mess created by punching through the slab.


However, in our experience, when done right—which we do—punching a hole in the slab does not compromise the integrity of your foundation. Not to mention, even foundation repair companies will punch a hole in the slab in certain situations. Why would they do this if it wasn’t safe?

And with our cleanliness guarantee, you won’t have to deal with a mess made by our crews.

So why then do these companies try to steer customers toward tunneling? Tunneling costs a lot of money which equals more money in the plumbing company’s pocket. So many companies will try to scare you into this unnecessarily expensive option.

Most homeowners will never have to deal with a fresh water leak. And if you do, it’s most likely you only have one. So once that leak is repaired, you shouldn’t have another leak. But if you do have another leak or multiple leaks, there is probably something wrong with the pipes.

In those cases, spot repair isn’t the best choice.


This option is what we recommend if you’ve had fresh water leaks before or if we find multiple leaks.

With repiping and rerouting, the pipes under the slab are abandoned. The plumber then reroutes new ones in the walls and attic.

Until recently, we strongly recommended against this option. There’s a lot of cosmetic repairs necessary with rerouting. We have to cut through the walls and maybe the ceiling. And plumbers only handle the plumbing so you will have to hire another company to fix the cosmetic issues.

Also if there is a problem with the lines and a pipe bursts or there is a leak, you risk water leaking into the house potentially causing a lot of damage.

However, as most houses are now built with the lines in the walls and ceiling, as time goes on, this is a moot point.

Trenchless Repair

The last option is trenchless. With trenchless, there is no digging, going through the slab, or cosmetic repairs. Instead, a liquid epoxy is pumped into the pipes and creates an inner coating which seals the leak or leaks.

We don’t offer or recommend trenchless repair. At one time, we referred customers interested in trenchless to a local company we had thoroughly researched and trusted. But after 12 years of providing trenchless repair, the company stopped offering this service for a number of reasons, one of which includes the long-term effectiveness of the repairs.

There are one or two companies in the DFW area who still offer trenchless. While we can’t recommend them, we strongly suggest you do your research into the companies and trenchless repair itself. Check out our guide on how to find a trustworthy plumbing company.

Give Us a Call

If you think you have a fresh water leak, above or under the slab, or have any questions or comments, feel free to leave it below this post! Or contact us today at 972-494-1750 or email at


In-House Plumbing Company

Get Sensible Solutions Today

Say goodbye to water or sewer leak issues, especially ones under your foundation, by putting our plumbing company to work for you. We offer timely, sensible solutions and restore peace of mind without significantly affecting your property or budget. Contact In-House Plumbing Company today to schedule an appointment.