Water Bill Doubled, Nothing Wet? Slab Leak Signs in Antioch

Your water bill arrived and it is double what it should be. You have checked under every sink, looked behind the toilets, walked the yard, and inspected the water heater. Everything is dry.

That combination — a bill that jumped with nothing visibly wrong — is the classic signature of a slab leak: a break in a water line running underneath or inside your home’s concrete foundation. The water has somewhere to go that you cannot see, which is precisely why it goes unnoticed until the bill arrives or the damage surfaces.

Slab leaks are common in Antioch for a specific reason. Most of the housing stock here is slab-on-grade construction, with copper supply lines run through or beneath the concrete. Add expansive Delta-area clay soil that shifts through the year and hard water moving through copper, and you have the conditions that produce them.

Run This Test Before You Do Anything Else

You can confirm a leak yourself in about twenty minutes, and it costs nothing.

1. Turn off every water-using fixture and appliance in the house. Dishwasher, washing machine, ice maker, irrigation timer — all of it.
2. Find your water meter, usually in a covered box near the street.
3. Look for the leak indicator: a small triangular, star-shaped, or gear-shaped dial on the meter face. Some meters do not have one, in which case write down the full reading.
4. If the leak indicator is moving with everything off, water is flowing somewhere. You have a leak.
5. No indicator? Record the reading, do not use water for two hours, and check again. Any change means a leak.

To narrow it down: find your main shutoff valve — typically where the supply enters the house, in the garage, or near the water heater — and close it. Then check the meter again. If the meter stops, the leak is inside the house or under the slab. If the meter keeps running with the main closed, the leak is in the service line between the meter and the house.

Seven Signs of a Slab Leak

1. A Water Bill That Jumped With No Change in Habits

A pinhole leak under a slab can waste substantial water continuously, day and night. Compare this month against the same month last year rather than against last month, so seasonal irrigation does not distort the picture.

2. The Sound of Running Water When Nothing Is On

Late at night, with the house quiet, listen near the floor. A faint hiss, rushing, or trickling with every fixture off is water escaping under pressure. This is often the first thing homeowners notice.

3. A Warm Spot on the Floor

This one is nearly diagnostic. Walk the house barefoot. An unexplained warm patch on a tile or vinyl floor means a hot water line is leaking beneath it and heating the concrete above. Hot water lines fail more often than cold ones, because heat accelerates corrosion and thermal cycling flexes the pipe.

4. Damp Carpet, Warped Flooring, or Bubbling Floor Covering

Water finds a path up through the slab. Look for carpet that is inexplicably damp in one area, hardwood cupping or lifting, vinyl bubbling or releasing from the floor, or grout darkening in a patch that never dries.

5. Cracks Appearing in Floors or Walls

Water escaping under a foundation erodes the soil supporting it. As that support washes away, the slab settles unevenly. New cracks in the floor, walls, or ceiling — or doors and windows that suddenly stick or will not latch — can signal a leak that has been running long enough to move the foundation.

6. Mildew Smell or Visible Mold

A musty odor with no obvious source, especially near the floor or in a closet, means persistent moisture. Mold under flooring or inside a wall base often shows up before any water does.

7. Reduced Water Pressure Throughout the House

If a meaningful share of your supply is escaping before it reaches your fixtures, pressure drops everywhere at once. Combined with any other sign on this list, it points to a leak rather than a plumbing restriction.

Why Slab Leaks Happen Here

• Expansive clay soil. Antioch sits on soil that swells and shrinks across the seasons, flexing the slab and stressing pipes embedded in or running beneath it.
• Abrasion. Copper vibrating against concrete or rebar as water flows will eventually wear through the pipe wall.
• Water chemistry. Hard water and certain mineral content corrode copper from the inside over decades.
• Hot water line stress. Repeated expansion and contraction fatigues the pipe, which is why hot lines fail first.
• Original installation. A pipe kinked, poorly supported, or laid in direct contact with concrete during construction fails decades ahead of schedule.

How Slab Leaks Are Located Without Tearing Up Your Floor

The critical skill is not repairing a slab leak. It is finding it precisely, so that repair means opening a small area rather than a large one.

Professional water leak detection uses several methods together:

• Acoustic listening equipment amplifies the specific sound of pressurized water escaping, isolating it from ambient noise.
• Thermal imaging reads temperature differences through the slab, which makes hot water leaks show clearly.
• Pressure testing isolates the hot and cold systems separately to determine which one is losing pressure.
• Tracer gas introduces a safe helium or hydrogen mix into the line; it escapes at the break and is picked up at the surface.
• Line tracing maps the actual route of the pipe under the slab before any concrete is touched.

Done properly, this narrows the leak to a small area — not “somewhere in the north half of the house.”

Your Repair Options

Spot repair. Open the slab at the located leak, repair the section, patch the concrete. Best for a single leak in an accessible spot on otherwise sound plumbing.

Reroute. Abandon the failed line under the slab and run a new line through walls or the attic instead. This avoids breaking concrete entirely and is often the practical choice when the leak sits under a kitchen island, a tiled bathroom, or anything expensive to restore.

Repipe. When there have been multiple slab leaks, the pipe under the foundation is at the end of its life and further spot repairs are throwing money at a system that will keep failing. A whole house repipe reroutes everything above the slab and ends the problem permanently.

A rough guide: a first slab leak in an otherwise healthy system is a spot repair. A second leak means it is time to seriously discuss rerouting or repiping.

Do Not Wait This One Out

Slab leaks are one of the few plumbing problems where delay reliably multiplies the cost. Water running under a foundation is eroding the soil that supports your house, and foundation repair is an order of magnitude more expensive than plumbing repair. Insurers also tend to look more favorably on damage that was addressed promptly than on damage that ran for months.

If your meter test showed movement, or you have a warm spot on the floor, call today rather than next month.

Get It Located Accurately

Service Pros Plumbers provides electronic leak detection throughout Antioch, Concord, and Walnut Creek, with 24-hour emergency availability and a 4.9-star rating across more than 1,000 reviews. We locate the leak precisely first — which is what keeps the repair small.

Our Antioch office is at 126 Railroad Ave.

Call (925) 753-5600 or request service online. CA License 979455.

Frequently Asked Questions

Does homeowners insurance cover a slab leak?

Many policies cover the resulting water damage and the cost of accessing the pipe, while excluding the pipe repair itself. Coverage varies significantly between policies, and gradual damage is often treated differently from sudden failure. Contact your carrier early — before repairs begin — and document everything.

Can a slab leak repair itself or stop on its own?

No. Pressurized supply lines do not heal. A leak that seems to have stopped has usually just found a different path through the soil, which means it is still running and still eroding.

How much water does a slab leak waste?

Even a pinhole under constant pressure runs continuously, which is why bills often double. The waste compounds every day the leak goes unaddressed.

Will I have to move out during the repair?

Usually not. A spot repair or reroute is typically completed within a day or two, with water off only briefly. Extensive foundation damage or mold remediation may require temporary relocation.

Is a slab leak the same as a foundation leak?

They are different problems that look similar. A slab leak is your pressurized water line failing beneath the concrete. Water intruding through the foundation from outside is a drainage or waterproofing issue. Leak detection distinguishes them, and the fixes are unrelated.