Signs You Have a Slab Leak in Your Boise Home

A slab leak is one of the most serious—and potentially expensive—plumbing problems a Boise homeowner can face. Because the leak is hidden beneath your concrete foundation, it can cause extensive damage before you ever notice a problem. Understanding the warning signs of a slab leak helps you catch the issue early, before it causes foundation damage, mold growth, or thousands of dollars in water waste. Here’s what every Boise homeowner needs to know.

What Is a Slab Leak?

A slab leak refers to a leak in the water supply or drainage pipes that run beneath or within your home’s concrete slab foundation. Many Boise homes—particularly those built from the 1960s through the 1990s in neighborhoods like the Bench, West Boise, and parts of Southeast Boise—are built on concrete slab foundations with copper water lines embedded in or running below the slab.

Over time, these pipes can develop leaks due to:

• Corrosion from Boise’s hard water reacting with copper pipes
• Abrasion from pipes rubbing against concrete, gravel, or rebar as the house settles
• Soil shifting caused by Boise’s clay-heavy soil expanding and contracting with moisture changes
• Age—copper pipes have a typical lifespan of 50–70 years, and many Boise slab homes are reaching that age
• Poor installation—kinked pipes, improper soldering, or insufficient protection during original construction

8 Warning Signs of a Slab Leak

1. Unexplained High Water Bill

If your water bill suddenly spikes without a change in usage, a hidden leak is a likely cause. A slab leak can waste hundreds or even thousands of gallons per month. Compare your current bill to the same period last year—if it’s significantly higher, investigate immediately.

2. Warm or Hot Spots on Your Floor

If you notice warm areas on your tile, laminate, or hardwood floors, you may have a hot water line leak under the slab. Walk barefoot across your floors—an isolated warm patch is a telltale sign, especially if it’s not near a heating vent or appliance.

3. Sound of Running Water When Everything Is Off

Turn off every faucet, appliance, and fixture in your home. Then listen carefully near the floor, particularly in bathrooms, kitchens, and utility areas. If you hear a hissing, whooshing, or running water sound, a pipe under the slab may be leaking.

4. Cracks in Your Foundation or Walls

Water from a slab leak saturates the soil beneath your foundation, causing it to shift and settle unevenly. This can produce visible cracks in your foundation, interior walls, or exterior stucco. While small hairline cracks are common in aging homes, new or widening cracks—especially combined with other signs on this list—warrant investigation.

5. Damp or Wet Carpet or Flooring

If carpet, hardwood, or laminate flooring is damp, warped, or buckled without an obvious source (no spills, no recent mopping), water may be seeping up through the slab from below. This often shows up as persistent dampness in a localized area.

6. Mold or Mildew Growth

Excess moisture from a slab leak creates ideal conditions for mold and mildew, especially under carpet, behind baseboards, and inside walls near the floor. If you notice mold growth or a musty smell near floor level, a slab leak may be the moisture source.

7. Decreased Water Pressure

A significant leak in your supply line reduces the water pressure at your fixtures. If your water pressure has gradually decreased—especially if it’s worse at specific fixtures—this may indicate a supply line leak under the slab.

8. Musty or Earthy Smell

Persistent musty or earthy odors near the floor, even after cleaning, can indicate hidden moisture from a slab leak. This smell often accompanies mold growth you can’t see, behind walls or under flooring.

Why Slab Leaks Are Common in Boise

Several factors specific to the Boise area make slab leaks more prevalent here than in many other regions:

Hard Water and Copper Pipe Corrosion

Boise’s water supply, sourced from the Boise River aquifer and surface water, has a hardness of approximately 8–12 grains per gallon. This hard water contains dissolved minerals—primarily calcium and magnesium—that accelerate corrosion in copper pipes. Over decades, this corrosion thins pipe walls from the inside, eventually creating pinhole leaks.

Soil Conditions

Much of the Boise area, particularly the Bench and West Boise, has clay-heavy soil that expands when wet and contracts when dry. This seasonal movement puts stress on under-slab pipes, creating friction points and potential failures.

Housing Age

A large percentage of Boise’s slab-foundation homes were built between 1960 and 1990 with copper water lines beneath or within the slab. These pipes are now 35–65 years old—well into the age range where corrosion-related failures become common.

Professional Slab Leak Detection Methods

Modern leak detection technology allows plumbers to locate slab leaks precisely without tearing up your entire floor. Here are the primary methods used:

Acoustic Detection

Specialized electronic listening equipment amplifies the sound of water escaping from a pipe under the slab. A trained technician can pinpoint the leak location by analyzing the sound pattern, often to within a few inches.

Thermal Imaging

Infrared cameras detect temperature variations on your floor surface. A hot water leak creates a warm zone that shows clearly on thermal imaging, even through tile, carpet, or hardwood.

Pressure Testing

By isolating sections of your plumbing system and monitoring pressure changes, a plumber can determine which line is leaking and narrow down the location. This is often the first diagnostic step.

Electronic Line Tracing

A transmitter sends a signal through the pipe, and a receiver traces the pipe’s path through the slab. This maps the pipe layout and helps pinpoint where the leak occurs along the line.

Slab Leak Repair Options

Once a slab leak is confirmed and located, there are several repair approaches:

Spot Repair

Cost: $800–$2,500

The plumber cuts through the slab at the leak location, repairs or replaces the damaged pipe section, and patches the concrete. This is the most affordable option when the leak is localized and the rest of the pipe is in good condition.

Pipe Reroute (Repipe)

Cost: $2,500–$6,000

Instead of repairing the under-slab pipe, the plumber abandons it and runs a new line through the walls, ceiling, or attic to bypass the slab entirely. This is often the best long-term solution if the pipe is old and likely to develop additional leaks. Learn more about our trenchless and non-invasive repair options.

Epoxy Pipe Lining

Cost: $1,500–$4,000

A flexible epoxy lining is inserted into the existing pipe, coating the interior and sealing leaks from the inside. This works for small leaks and can extend pipe life by 10–20 years, but isn’t suitable for severely damaged pipes.

Full Repipe

Cost: $5,000–$15,000

If multiple under-slab pipes are compromised, a full repipe replaces all water lines with new piping (typically PEX) routed through walls and ceilings, completely bypassing the slab. This is the most expensive option but provides a long-term, worry-free solution.

What to Do If You Suspect a Slab Leak

1. Check your water meter. Turn off all water in your home, then check if your water meter is still running. If it is, you have a leak somewhere.
2. Document the signs. Note which symptoms you’re experiencing, where on the floor you notice them, and when they started.
3. Call a professional. Slab leak detection and repair requires specialized equipment and expertise. Don’t attempt to break through your slab without a professional diagnosis.
4. Contact your insurance company. Many homeowner’s policies cover sudden slab leak damage. File a claim early in the process.

Frequently Asked Questions

How much does slab leak repair cost in Boise?

Slab leak repair in Boise typically costs $800–$6,000, depending on the repair method. A localized spot repair is the least expensive ($800–$2,500), while a full pipe reroute costs $2,500–$6,000. Professional leak detection adds $200–$500 to the total. If the slab leak has caused water damage, mold, or foundation issues, total restoration costs can be significantly higher.

Does homeowner’s insurance cover slab leaks in Idaho?

Most Idaho homeowner’s insurance policies cover damage caused by a sudden slab leak (water damage to flooring, walls, and personal property), but typically do not cover the cost of repairing the pipe itself. Damage from gradual leaks that you should have noticed may not be covered. Contact your insurance agent as soon as you suspect a slab leak to understand your coverage.

How long can a slab leak go undetected?

A slab leak can go undetected for months or even years, especially if it’s a small, slow leak. During that time, it can waste thousands of gallons of water, erode soil beneath your foundation, promote mold growth, and cause gradual foundation settling. This is why it’s important to investigate any unexplained changes in your water bill, floor temperature, or water pressure promptly.

Can I detect a slab leak myself?

You can identify the warning signs of a slab leak (listed above), but pinpointing the exact location requires professional equipment. The most useful DIY check is the water meter test: turn off all water in your home, note the meter reading, wait 2 hours without using any water, and check the meter again. If it has moved, you have a leak somewhere in your system.

---

Think you might have a slab leak? Hyde Park Plumbing offers professional leak detection services using acoustic, thermal, and electronic methods to find leaks with minimal disruption to your home. Call us at (208) 994-3745 for fast, accurate diagnosis. We serve the entire Boise metro area.