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• March 14, 2025

Plumbing Tips

How to Find a Water Leak Underground: Signs & Detection

Underground water leaks can be costly, damaging, and difficult to detect. If left unaddressed, they can lead to increased water bills, foundation damage, mold growth, and even structural issues. While some signs may indicate a hidden leak, accurately locating the source requires a combination of DIY methods and professional techniques. Read on to learn How to Find a Water Leak Underground.

This guide will help you identify the signs of an underground water leak, explore detection techniques, and determine when to seek professional assistance to fix it. By following these steps, you can prevent water loss, save on costly repairs, and protect your property.

Common Signs of an Underground Water Leak

Detecting a water or gas leak underground starts with recognizing the warning signs. Since these leaks are not immediately visible, homeowners must look for indirect clues.

1. Unexplained Increase in Water Bills

If your water bill has suddenly increased without a change in usage, it may indicate a hidden leak underground. Compare your recent bills to past months and look for a consistent spike in water usage.

Compare bills over several months to identify unusual increases.
Shut off all water sources and check if the meter still moves.
Inspect areas around water lines for unexpected dampness.

2. Low Water Pressure

A decrease in water pressure across multiple fixtures in your home can be a symptom of an underground leak. When water is escaping before reaching your faucets, you may notice weaker water flow, slow-filling appliances, or irregular fluctuations in pressure.

Test water pressure in different areas of your home.
Look for consistent pressure drops over time.
Check for leaks in exposed pipes and fixtures before suspecting an underground issue.

3. Wet Spots or Sinkholes in the Yard

If certain areas of your yard remain wet or muddy even in dry weather, this could signal an underground pipe leak. In severe cases, water leakage can erode soil, leading to depressions or sinkholes forming near your house or water line.

Inspect your yard for consistently damp or muddy patches.
Check for unusual depressions or sinkholes forming near water lines.
Monitor plant growth, as excessive moisture may cause overgrown patches.

4. Mold Growth or Musty Odors

Hidden moisture from underground leaks can create an ideal environment for mold and mildew. If you detect a musty smell or notice mold patches indoors, this could be a sign of excess moisture from a leaking water line.

Check for mold growth on walls, ceilings, and floors, particularly in lower levels.
Pay attention to persistent musty odors that don’t go away with cleaning.
Inspect baseboards and carpets for signs of moisture damage.

5. Water Meter Running When No Water is Used

A simple DIY test is to check your water meter. Turn off all water sources in your home, then monitor the meter reading. If it continues to move, there’s likely a leak somewhere in your plumbing system, possibly underground.

Shut off all faucets, appliances, and irrigation systems before testing.
Observe your water meter for movement over a 15-30 minute period.
Take note of any changes in meter readings and compare them over time.

DIY Methods to Detect an Underground Water Leak

Before calling a professional, there are several methods you can use to determine if a leak exists and where it might be located. These methods range from simple observational techniques to hands-on testing that can help identify potential underground leaks.

Checking the Water Meter

Begin by shutting off all water usage inside and outside your home. Locate your water meter and observe the dial. If it moves, even when no water is running, this indicates a leak. For slow leaks, take a meter reading, wait two hours without using water, and check the reading again.

Ensure all faucets, appliances, and irrigation systems are turned off before checking the meter.
Record the initial reading, wait a few hours, and compare it to the new reading.
If the reading changes despite no water usage, this suggests a possible leak in the system.

Listening to Unusual Noises

Underground waste water leaks often produce a hissing or rushing sound. At night, when external noise is minimal, listen closely near pipes or drains for any unusual sounds that may indicate a leak.

Use a simple stethoscope or a long screwdriver pressed against the pipe to amplify sounds.
Focus on areas where the plumbing runs underground, such as near outdoor spigots or main water lines.
Compare sound levels at different points to pinpoint possible leak locations.

Testing with Food Coloring

This method is useful for identifying leaks in toilets, which can contribute to underground water loss. Add food coloring to the toilet tank drain and wait 15-30 minutes. If the color appears in the bowl without flushing, there is a leak that may be impacting your overall water usage.

Choose a dark-colored food dye for better visibility.
Perform this test on all toilets in the home to rule out multiple leaks.
If leakage is detected, replace the flapper valve or internal tank components as needed.

Performing a Pressure Test

Attach a pressure gauge to an outdoor faucet and turn off the main water supply. If the pressure drops significantly within 15 minutes, it could indicate a leak somewhere in your underground pipes.

Purchase a pressure gauge from a hardware store and attach it securely to an outdoor spigot.
Close all water-using appliances and fixtures before testing.
If pressure drops significantly, consult a professional to further investigate the leak’s location.

Advanced Leak Detection Techniques Used by Professionals

For precise leak location, professionals use specialized equipment that minimizes the need for unnecessary digging. These advanced techniques help detect leaks with greater accuracy, reducing costly excavation and repairs. By leveraging specialized tools, professionals can also prevent water damage and protect structural integrity.

Acoustic Leak Detection

This method involves using sensitive listening devices to detect sound variations caused by water escaping under pressure. Professionals can pinpoint and find underground water leaks by analyzing noise patterns underground. This technique is especially effective for detecting leaks in large water distribution systems and municipal pipelines. The accuracy of acoustic leak detection depends on factors such as pipe material, soil type, and water pressure.

Infrared Thermal Imaging

Thermal cameras detect temperature changes in the ground or walls, revealing moisture buildup from hidden leaks. This non-invasive method is effective for locating underground leaks without excavation. By detecting temperature differences, thermal imaging can help distinguish between leaks and naturally occurring groundwater. Additionally, this technique is particularly useful in detecting leaks beneath concrete slabs and other hard surfaces where traditional methods may be ineffective.

Ground Penetrating Radar (GPR)

GPR technology uses electromagnetic waves to scan beneath the surface and locate leaks in underground water lines. It is particularly useful for identifying leaks under concrete, asphalt, or soil. This method provides highly detailed subsurface images, allowing professionals to distinguish between different types of underground materials. Additionally, GPR is a non-destructive testing technique, making it ideal for preserving infrastructure while accurately detecting leaks.

Soil Moisture Sensors

These devices measure soil saturation levels, helping professionals and water companies identify areas where excessive moisture suggests a leak. By analyzing moisture patterns, these sensors can help pinpoint leak locations with greater precision. They are particularly useful in large-scale leak detection projects, such as municipal water systems and agricultural irrigation networks.

What Causes Underground Water Leaks?

Understanding the root causes of underground leaks can help prevent future damage.

Aging Pipes & Corrosion

Pipes naturally degrade over time, leading to leaks due to rust, cracks, or weak joints. Older homes with metal pipes are especially prone to corrosion-related leaks.

Soil Shifts & Ground Movement

Seasonal weather changes, earthquakes, or construction activity can shift soil, putting stress on pipes and causing fractures.

Tree Root Intrusion

Tree roots naturally seek out moisture, often infiltrating underground water lines. Over time, roots can wrap around pipes, break them, or cause blockages.

Poor Installation or Construction Damage

Incorrectly installed pipes or accidental damage from digging during construction projects can lead to leaks. Always ensure proper pipe installation and monitor any ground disturbances.

When to Call a Professional for Leak Detection

While some leaks can be found using DIY methods, professional assistance is often necessary for accurate detection and repair.

If you cannot locate the exact source of the leak.
If there are major fluctuations in water pressure.
If wet spots or sinkholes appear on your property.
If your water bill continues to rise despite efforts to conserve water.

Professional leak detection services use non-invasive tools to find leaks, minimize property disruption, and expedite necessary repairs.

Conclusion: How to Find a Water Leak Underground

Detecting an underground water leak early can save money, prevent structural damage, ensure safety, and reduce water waste. By using DIY methods or consulting professionals with advanced detection equipment, you can efficiently locate and repair leaks before they escalate into costly issues. If you suspect an underground leak, take action today to protect your property and ensure the integrity of your plumbing system.

For expert assistance, Prestige Water Group provides professional leak detection, plumbing installation, repair, and maintenance across New Jersey. Our team uses cutting-edge tools and years of expertise to quickly diagnose and resolve underground water leaks. Whether you’re upgrading to a tankless unit or servicing your current system, our licensed professionals are ready to help. Call (973) 227-4740 or email info@pwgroupnj.com to schedule an appointment. Visit our website for more details on our plumbing and water treatment services.

FAQ: How to Find a Water Leak Underground

What is the best way to find a water leak underground?

The best method depends on the severity and location of the leak. Start by checking your water meter, inspecting for wet spots, and listening for unusual noises. If unsure of exact location, hire a professional to use acoustic detection, infrared imaging, or GPR technology.

Is there a tool to detect a water leak?

Yes, professionals use tools like acoustic leak detectors, infrared cameras, moisture meters, and ground-penetrating radar to locate hidden leaks without excavation. These technologies enable accurate leak detection while minimizing property damage.

How to detect a leak in an underground pipe?

Turn off all water sources and monitor your water meter. Check for persistent wet spots in your yard that don’t dry up, even in warm weather. Listen for unusual sounds of running water where pipes are buried. Additionally, consider using a pressure test to confirm if a leak is present in your underground plumbing system.

How do I find a water leak that is not visible?

If a leak is not visible, check for indirect signs such as high water bills, low pressure, or damp areas. Look for unexplained wet spots in your yard or foundation cracks that could indicate water seepage. If necessary, contact a professional to conduct advanced leak detection using specialized equipment.