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How to Tell if You Have an Underground Water Leak

It’s every homeowner’s or building owner’s worst nightmare. An underground water leak, sometimes also called a slab leak, is a leak originating from the water pipes that run under your home or building. These leaks are a bit harder to detect and when left untreated and can lead to fairly extensive damage. Damage ranges from your personal possessions to the structural integrity of your residence. Either way, an underground water leak is no fun. 


Want to avoid running into this headache? Keep reading to discover the signs of an underground leak so your home or building will remain leak and trouble-free.

8 Ways to Tell if You Have a Water Leak Underground

Since it’s underground, this kind of water leak can often go unnoticed for months (or even years) if it’s a slow enough leak. As homeowners, it is crucial to conduct regular inspections of your home’s plumbing, both inside and outside. This means checking the areas around all plumbing fixtures for signs of moisture on a regular basis. 


If something doesn’t seem right, an underground water leak could be to blame. 


Underground leaks are often the result of pinholes in pipes due to friction or corrosion, erosion, expansive soil shift, poor quality pipes or installation, poor water quality or chemistry, and age. Homes that are older than 15 years are more susceptible to underground leaks.


How do you know you could be dealing with one? Here are some of the biggest tell-tale signs:

  • Low water pressure

  • Water meter running after the water has been turned off in the house

  • Increased water usage and high water bill

  • Puddles in the lawn

  • Excess water in the soil around the home/noticeable muddy areas

  • Cracks in the foundation

  • Water sounds when water isn’t running in the home

  • Damp flooring or walls

To understand these a little more and what specifically to look for, let’s take an in-depth look at each below.

Low Water Pressure in Home

If you experience a drop in your water pressure, especially a sudden drop, this could be an indication that there is a leak. If you experience a loss of water pressure in a single fixture or faucet, it could be a sign of a leak. But if you experience the loss of pressure throughout your entire home, it’s an indication that you may have an underground water leak.

Check Your Water Meter

One of the easiest ways to determine if you have an underground water leak is to look at the water meter. Turn off all the water in the home, ensuring no faucets are running. Double-check that the dishwasher, filter systems, toilets, and washing machine aren’t running either. Ideally, you’ll use the shutoff valve at the water main to turn your water supply completely off.


Then, watch the meter and look for it to change. If you see a change, there is most likely a fast leak. If you don’t see the meter changing immediately, that doesn’t mean you’re in the clear. Wait thirty minutes without running any water in the home, and check it again. If it has changed even though the water is off, you’re likely dealing with a slow leak. 


The leak could be anywhere after the meter, sometimes it can even be found underground. All the piping from the meter to the home is the homeowner’s responsibility.

Look at Your Bill and Usage

According to the Environmental Protection Agency (EPA), you should check your water usage in a colder month. If a family of four uses more than 12,000 gallons of water in a month, it might be a sign that there are serious leaks.


Keep a special eye on your bill and make note of any major changes. If you notice the water bill is continuing to go up but you cannot find a clear reason for the increase, take some steps to determine if it’s a leak. 


This could mean putting food coloring in your toilet tank to see if it’s leaking, checking faucets, inspecting your water heater, and other quick testing methods. If there’s a steady increase every month for a few months, there’s most likely a leak somewhere in the home.

Puddling in Lawn

If you spot any kind of standing water in your yard and it’s not during a rainy season, there are a number of potential reasons for it. Poorly draining soil is one of the most common causes of puddles. And when there is a lot of water because of a leak underground, even soil that drains well will reach a point where it cannot hold any more water. This will cause the ground and soil to begin swelling and puddling. And the longer the water stands there, the more potential damage can occur. 


Not only are you possibly dealing with an underground leak, but the standing water is also a perfect breeding ground for mosquitoes. Eventually, grass will stop growing, and moss is more likely to take its place.

Excess Water in the Soil Around Home

If you notice the soil around your home is unstable because of increased moisture (and of course, there hasn’t been any rain recently), that could indicate an underground pipe leak. The soil around the leak is often saturated with water, which causes greener grass. If you suspect an issue, try digging a hole in the soil around where you suspect the leak is. The hole itself will fill with water. 


Soil saturated with water quickly destabilizes. As a result, it can crack any pavement near your home, and could lead to potholes in the concrete and, even worse, sinkholes on your property. Ignoring the issue could result in thousands of dollars in costly repairs.

Crack in Foundation

If there’s a water leak under the concrete slab your home sits on, the leaking water can seep into the foundation and cause cracks. If left to continue leaking for an extended period of time, this can weaken the overall structure of your home and can even result in cracks in the walls. Make it a point to regularly check your foundation for cracks and other signs of moisture. 


If you find a crack, call a plumber or trained professional to come out for a more extensive inspection as soon as possible.

Water Sounds

If you hear what sounds like running water when you know it’s not running anywhere in the home, that’s a sure sign of a leak somewhere. You may also hear whistling, dripping, hissing, or spraying sounds in the pipes.

Damp Flooring or Walls

If you notice the floor seems to be a bit damp or notice dampness in your drywall, that’s an alarm. You may even start to smell mildew or see mold if the leak has been active for an extended length of time. If you also feel warmth in certain areas of the floor, this could mean the leak is in the hot water lines.


Remember, your homeowner’s insurance will likely cover the cost of most water damage, but will probably not cover the cost of complete pipe repair. 


To maintain continuous coverage, your insurance company may require proof of the repair. The sooner you take action, the better.

Need Help?

If you believe you have an underground water leak in your home, contact us right away. We’re available 24/7 for emergency services in your home, office, or other commercial building.

Our leak detection technology can help quickly locate the source and develop the repair plan before any severe damage or issues arise. We also have financing options available to help you every step of the way.

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