How to Tell If You Have an Underground Water Leak | 8 Warning Signs

An underground water leak can be one of the most stressful plumbing problems for a homeowner or building owner. Also known as a slab leak, this type of leak usually comes from water pipes running below a home, building, yard, or concrete slab.

Because underground leaks are hidden, they can be difficult to spot early. If left untreated, they may damage flooring, walls, personal belongings, landscaping, and even the structural integrity of the property.

The good news is that underground leaks often leave warning signs. Knowing what to look for can help you act quickly before the damage becomes more serious.

8 Signs You May Have an Underground Water Leak

Underground water leaks can go unnoticed for months or even years, especially if the leak is slow. Regular plumbing inspections inside and outside your property can help catch problems early.

Common causes of underground leaks include:

• Pipe corrosion
• Pinholes caused by friction
• Soil movement or expansive soil
• Erosion
• Poor pipe installation
• Low-quality piping materials
• Poor water quality or water chemistry
• Aging plumbing systems

Homes older than 15 years may be more vulnerable to underground leaks. Here are eight warning signs to watch for.

1. Low Water Pressure

A sudden drop in water pressure can be a sign of a hidden leak. If only one faucet or fixture has low pressure, the issue may be isolated. But if the entire home experiences reduced water pressure, an underground water leak may be the cause.

When water escapes from a pipe before it reaches your fixtures, the system may not maintain normal pressure.

2. Water Meter Running When Water Is Off

One of the easiest ways to check for a possible underground leak is to inspect your water meter.

First, turn off all water inside the home. Make sure faucets, toilets, the dishwasher, washing machine, water filters, and other water-using appliances are not running. Ideally, shut off the water supply at the main valve.

Then watch the meter.

If the meter changes immediately, you may have a fast leak. If it does not move right away, wait about 30 minutes without using any water and check again. If the meter changes while the water is off, there may be a slow leak somewhere after the meter.

In many cases, the piping from the meter to the home is the homeowner’s responsibility.

3. Increased Water Usage or a High Water Bill

A rising water bill is often one of the first clues that something is wrong. If your usage increases but your household habits have not changed, there may be a leak.

The EPA recommends checking water usage during colder months. If a family of four uses more than 12,000 gallons in one month, that may indicate a serious leak.

Before assuming the leak is underground, check common sources such as toilets, faucets, water heaters, irrigation systems, and visible plumbing fixtures. If usage keeps climbing and you cannot find the cause, it may be time for professional leak detection.

4. Puddles or Standing Water in the Lawn

Standing water in your yard when it has not rained may point to an underground pipe leak.

Poor drainage can cause puddles, but a buried water line leak can oversaturate the soil until it can no longer absorb water. This may create puddles, swollen soil, muddy areas, or unusually soft ground.

Standing water can also attract mosquitoes, damage landscaping, and eventually cause grass to stop growing.

5. Excess Water in the Soil Around the Home

If the soil around your home feels unusually wet, unstable, or muddy without recent rain, there may be a leaking pipe underground.

In some cases, the grass above the leak may look greener because the soil is constantly saturated. If you dig near the suspected leak area and the hole fills with water, that may be another warning sign.

Oversaturated soil can destabilize the ground, crack pavement, damage concrete, and in severe cases contribute to sinkholes or foundation problems.

6. Cracks in the Foundation

A leak beneath a concrete slab can allow water to seep into the foundation. Over time, this moisture can cause cracks, weaken the structure, and even lead to wall damage.

Check your foundation regularly for cracks, moisture, or unusual shifting. If you notice new or expanding cracks, contact a plumber or trained leak detection professional as soon as possible.

7. Running Water Sounds When No Water Is On

If you hear running water when no faucets, appliances, or fixtures are being used, there may be a hidden leak.

Other sounds that may indicate a leak include:

• Dripping
• Hissing
• Whistling
• Spraying
• Water movement inside walls or floors

These sounds can come from pressurized water escaping through a pipe.

8. Damp Flooring, Walls, Mold, or Mildew

Damp floors, wet drywall, mildew smells, or visible mold can all point to an underground or slab leak.

If the leak involves a hot water line, you may also notice warm spots on the floor. Moisture that remains hidden for too long can lead to mold growth, flooring damage, and costly repairs.

Homeowner’s insurance may cover certain water damage, but it may not cover the full cost of pipe repair. Your insurance company may also require proof that the leak was properly repaired to maintain coverage.

What to Do If You Suspect an Underground Water Leak

If you think you have an underground water leak, do not wait. The sooner the leak is located, the easier it may be to prevent major water damage, structural problems, and expensive repairs.

Professional leak detection technology can help locate the source of the problem without unnecessary digging or demolition. Once the leak is found, a repair plan can be created for your home, office, or commercial building.

Need Help With an Underground Water Leak?

If you believe you have an underground water leak, contact us right away. We offer 24/7 emergency service for homes, offices, and commercial buildings.

Our leak detection technology can help quickly locate the source of the leak and develop a repair plan before more serious damage occurs. Financing options are also available to help you every step of the way.