Hidden water leaks are one of the more frustrating problems a homeowner can face — the damage accumulates steadily while the source stays out of sight. The most common warning signs include unexplained spikes in your water bill, the sound of running water when no fixture is in use, soft or discolored spots on walls or ceilings, and mold or musty odors in areas that should be dry. Catching them early prevents serious structural damage and mold remediation costs.

Your Water Bill Is Climbing for No Clear Reason

A water bill that jumps noticeably month over month — without a change in household habits, seasonal irrigation, or new appliances — is one of the most reliable early signals. Even a small pinhole leak in a supply line inside a wall can waste thousands of gallons per month. Compare your current bill to the same period from the prior year, accounting for seasonal use. If the numbers don’t match up, a leak is worth investigating.

You can do a quick check yourself: turn off every fixture, appliance, and irrigation zone in the house, then watch your water meter for 30 minutes without using any water. If the meter moves, water is flowing somewhere it shouldn’t be.

Sounds of Running Water With No Fixture On

If you hear the sound of water trickling, dripping, or running inside walls, floors, or ceilings when every faucet and toilet is off, that sound is coming from somewhere. A running toilet can mimic this — do a simple food coloring test in the tank to rule it out. If the toilet isn’t the culprit, you may have a pressurized supply line leak inside the wall or under a slab.

Soft Spots, Discoloration, or Bubbling on Walls and Ceilings

Paint that’s bubbling, peeling, or staining brown is absorbing moisture from behind the surface. Drywall that feels soft, spongy, or is visibly warped has been wet long enough to degrade. These are signs that a leak has been present for some time — not just a drip, but sustained moisture behind the wall.

In Colorado’s dry climate, materials dry out between wet events, which can make these signs intermittent and easy to dismiss. But if you’re seeing staining that returns after a dry period, moisture is coming from inside — not condensation or a one-time spill.

Mold, Mildew, or Musty Odors

Mold can grow behind walls, under flooring, and inside cabinets without being visible. A persistent musty smell in a specific area of the house — especially a bathroom, laundry room, or kitchen — often indicates moisture accumulation. Denver’s low humidity means mold doesn’t grow easily from ambient air alone; if you’re smelling it, there’s typically a water source sustaining it.

  • Unexplained water bill increase without a change in usage habits
  • Water meter moving when all fixtures and irrigation are off
  • Sound of running or dripping water inside walls or floors
  • Staining, bubbling, or soft spots on walls, ceilings, or floors
  • Mold growth or musty odor in normally dry areas
  • Warm or damp spots on flooring (can indicate a slab leak)

Warm Spots on the Floor: A Slab Leak Signal

In homes with hot water lines running under a concrete slab — common in ranch-style homes throughout the Denver metro — a hot water line leak creates a warm or hot spot on the floor above it. You might also notice the hardwood or laminate flooring buckling in a localized area. Slab leaks are serious; the water erodes the soil under the foundation and can cause settlement over time.

If you’re seeing any of these signs, don’t wait. Done’s plumbers use electronic leak detection and camera equipment to locate hidden leaks without unnecessary demolition. Visit our pipes and water lines page to learn about leak detection and repair, or call emergency plumbing if you suspect an active leak that’s causing damage right now.