What Are the Signs of a Slab Leak?
Signs of a slab leak include unexplained water bill increases, the sound of running water when fixtures are off, warm or damp spots on floors, new cracks in walls or foundation, and mold or mildew odors. Slab leaks are common in Phoenix due to shifting clay soils and hard water corrosion. Early detection is critical to prevent foundation damage.
Common Causes
Unexplained Increase in Water Bill
One of the earliest and most reliable signs. Even a small slab leak can waste thousands of gallons per month. If your bill jumps 20-30% with no change in usage, a leak is likely.
Sound of Running Water
When all fixtures are off, you shouldn't hear water running. A constant hissing, splashing, or running water sound, especially from floors or walls, often indicates a slab leak.
Warm or Damp Spots on Floors
Hot water line leaks create warm spots on tile, concrete, or carpet. You may also notice damp or wet areas. Pets often lie on these warm spots, watch where they choose to rest.
Cracks in Walls, Floors, or Foundation
Water from a slab leak erodes soil beneath your foundation, causing shifting and cracking. New cracks in walls, floors, or baseboards that appear suddenly warrant investigation.
Mold, Mildew, or Musty Odors
Constant moisture from a slab leak creates ideal conditions for mold growth. You may smell mildew before you see any visible signs, especially in closets or near baseboards.
Low Water Pressure Throughout House
A significant slab leak diverts water before it reaches your fixtures, causing pressure drops throughout the home. If pressure is low everywhere, not just one fixture, check for leaks.
Water Heater Running Constantly
If your hot water line has a slab leak, you're constantly losing hot water. Your water heater will run more frequently to keep up, increasing energy bills.
What Should You Do?
Try This First
- Turn off all water fixtures and appliances, then check your water meter, if it's still moving, you have a leak
- Walk barefoot on tile or hard floors to feel for warm or damp spots
- Check your water bill for unexplained increases over the past few months
- Look for new cracks in walls, floors, or the foundation exterior
- Listen near floors and walls for sounds of running water when nothing is on
Call a Pro If...
- Your water meter moves when all fixtures are off
- You've found warm spots, damp areas, or new cracks
- Your water bill has increased without explanation
- You smell mold or mildew but can't find the source
- Multiple signs from this list are present