How to tell if you have a water leak underground.

What happens if you have an underground leak?

An underground leak can cause severe water damage to your home. Over time, water damage may result in mold growth and structural damage. If you ignore an underground water leak, you may be looking at even more costly repairs.

In addition to flooding your yard and creating sinkholes, underground leaks can damage your home’s foundation. Water leaking from an underground pipe can cause the soil to shift and settle. If the ground shifts enough, cracks may form in the foundation. If you leave it for too long, foundation damage can be catastrophic — and maybe even irreversible.

In this guide, we'll walk you through some of the biggest signs that indicate you may have a water leak underground. 

1. High water bill.

The first sign of an underground link may be a high water bill. Keep an eye open for unexpected spikes in water usage. A sudden increase could indicate you're wasting gallons of water due to a leak somewhere underground. 

It’s important to note that a high water bill can result from several issues. For example, it could be a leaky toilet or faucet inside the house or an issue with your water softener. However, there are ways you can determine whether the leak is inside or outside your home. Follow these steps to narrow down the source of the leak:

• Find the water shut-off valve. Your home should have a valve to turn off the flow of water. There are a few places it could be, but common locations are the basement, garage and outside.
• Turn your water off. Closing the valve will cut off your home’s running water supply. Make sure the water is off by turning on a faucet inside the house.
• Watch the dial on the water meter. Once you’re sure your home’s water supply is off, check the dial. If it keeps moving, the leak is somewhere outside your home — possibly underground or in your irrigation system. If you shut off your valve to the house as well as the water to your irrigation system, but the dial is still moving, you may have an underground water line leak.

Visit the Saving Water Partnership website for more tips on how to use your water meter to check for leaks. 

2. Low or inconsistent water pressure.

When you have an underground water leak, the water loses pressure before it reaches your home. The flow of water from your faucets may be slower than usual, too.

If you notice a drop in water pressure from your faucets or shower heads, hire a plumber to check for an underground leak. If only one fixture has lowered pressure, the leak is probably somewhere in your home rather than underground.

3. Strange sounds from your pipes.

If you have an underground leak, you may notice odd noises when no taps or appliances are in use. A leak in an underground water pipe can result in hissing or splashing noises in your walls.

Listen carefully when you aren’t using any water. If your plumbing system is still making sounds, water is probably flowing somewhere it shouldn’t be — and it’s time to contact a plumber.

Related: Weird sounds and smells in your home you should never ignore.

4. Unusually green grass and water pooling on your lawn.

In some cases, underground leaks are bad enough to create large puddles. Keep an eye out for wet spots in your yard. If there are puddles when it hasn’t rained recently, an underground leak could be the cause. 

Also, look for unusually green or lush areas compared to the rest of the lawn. Isolated spots of unusual growth might indicate a leak.

5. Foul odors.

Another sign of an underground water leak is an unpleasant smell of mold or sewage. When an underground pipe leaks, waste from your home may not flow to the right place. As a result, a strong sewage smell may come from your home's drains. 

Improper water flow can also allow mold to form in your pipes. The combination of darkness and moisture makes a leaky pipe a welcoming environment for mold to thrive. 

A foul odor from your drain can have a few causes. To determine whether the smell is from an underground leak, check all the drains in your home. If all the drains smell of sewage, it’s probably an issue with the main water supply line. However, if only one drain has an odor, there’s likely a leak or blockage in that drain. 

Don’t wait to have the problem inspected if your underground leak is causing a foul odor. If sewage or mold enters your water supply, it could be a health hazard. Bacteria from mold and waste in your tap water can lead to a host of waterborne illnesses.

Related: How much does a plumber cost?

6. Discolored tap water.

If the water from your tap is dark or rust-colored, it might be a sign of a leak underground. When an underground pipe springs a leak, dirt or rust can enter your water supply. If running cold water doesn’t clear the discoloration after a few minutes, a leak is more likely the cause.

7. Sinkholes in your lawn.

When water leaks from an underground pipe, it saturates the surrounding soil. This saturation may cause the soil to sink. If you see sunken spots in your yard, it’s a sign that water may be eroding the soil. These small spots or holes are a tripping hazard and make it more difficult to maintain your yard.

It takes a large underground leak to cause sinkholes. If you find a sinkhole formation, the pipe has probably been leaking for some time. 

Act quickly to prevent permanent damage to your yard or home. Hire a pro to locate and fix the leak before it worsens.

8. Damaged paving.

An underground leak may also damage concrete slabs and paved areas, like a driveway or patio. The soil may shift and sink. And if the leak is near a paved area, the shifting soil can upset the concrete or asphalt. The paved surface will then crack or crumble above the saturated soil.

Hire a plumber near you.

If you think you might have an underground water leak, you should act fast. Download Thumbtack today to get free cost estimates from plumbers near you.