5 Signs You Have a Slab Leak (And What To Do Immediately)

A slab leak is one of the most serious plumbing problems a Fresno homeowner can face. Water escaping from pipes beneath your concrete foundation doesn't just waste water — it silently erodes soil, cracks slabs, breeds mold, and can cause tens of thousands in structural damage before you ever see a drop on the surface. Here are the five warning signs to watch for, and exactly what to do if you spot them.

1. Your Water Bill Jumped for No Reason

If your water usage hasn't changed but your bill climbed 20–50%, suspect a leak. A slab leak can waste 100+ gallons per day without any visible evidence. Compare your bill month-over-month and call a plumber if you see an unexplained spike. You can also do a quick check: turn off all water in your home and watch your water meter. If the dial keeps moving, water is escaping somewhere — possibly under your slab.

2. You Hear Running Water When Nothing Is On

Stand in a quiet room — kitchen, hallway, or bathroom — and listen. A faint hissing, rushing, or trickling sound when all faucets and appliances are off is a red flag. This is often most noticeable near the floor or baseboards, since the sound travels up through the concrete and walls. Don't dismiss this as pipes settling — pipes don't make running water sounds unless water is running.

3. Hot Spots or Damp Areas on Your Floor

Walk barefoot across your tile or hardwood floor. A circular warm spot — especially in an area far from any heat source — often indicates a hot water line leaking beneath the slab. Cold or wet spots can signal a cold water line leak. On carpet, look for sections that stay damp or develop a musty smell even without any surface spill.

4. Cracks in Walls or Flooring

As water erodes the soil and base material under your foundation, the slab shifts. This movement shows up as cracks — in drywall, along door frames, in floor tiles, or in the foundation itself. New cracks that appear suddenly or grow over weeks deserve immediate attention. In Fresno's expansive clay soil, foundation movement from any cause is magnified.

5. Low Water Pressure Throughout the House

A significant leak reduces the pressure available to your fixtures. If you notice weak flow at multiple faucets simultaneously — not just one — and it persists after checking the main shut-off valve, a supply line leak under the slab could be the cause.

What To Do Right Now

1. Turn off your main water supply valve if you suspect an active leak. This stops the damage from progressing.
2. Document everything — take photos of any wet spots, cracks, or damaged flooring. Your homeowner's insurance may cover slab leak repairs.
3. Call a plumber immediately. Slab leaks do not resolve on their own. Every hour of delay is additional damage to your foundation, subfloor, and walls.

How Stedman's Detects Slab Leaks

We use electronic leak detection and thermal imaging to pinpoint the exact location of a leak without tearing up your entire floor. Once located, we offer multiple repair options — direct-access spot repair, epoxy pipe lining, or full repiping — and we'll walk you through the pros and cons of each before any work begins.