You likely have a slab leak if your water bill jumps with no change in usage, you hear water running when every fixture is off, or a section of your floor feels warm or damp. Shut off every fixture and watch the water meter. If the dial still moves, water is escaping somewhere, and under-slab supply lines are the most common hidden culprit in Fort Collins homes.
What a slab leak actually is
A slab leak is a break or pinhole in a water supply line running underneath (or inside) the concrete foundation of your home. Because those lines are buried in or below the slab, the water has nowhere obvious to go. It soaks into the soil, wicks up through the concrete, or travels along the footing until it surfaces somewhere that looks unrelated to the actual break.
In Northern Colorado, most slab leaks we repair fall into two groups: copper supply lines installed between the late 1970s and the mid-1990s that develop pinhole corrosion from hard water, and lines that fracture when expansive clay soils shift after a wet spring or a hard freeze-thaw cycle.
The seven most reliable warning signs
No single symptom proves a slab leak, but two or three together almost always do. Walk your home and check for the following:
- A water bill that climbs 20% or more with no change in household usage.
- The sound of running or trickling water when every tap, toilet and appliance is off.
- Warm or hot patches on a tile or laminate floor, a sign the hot-water line is the one leaking.
- Carpet or baseboard that stays damp, or flooring that cups, buckles or lifts.
- A musty, mildew smell near the floor in one room that never clears.
- Persistently low water pressure throughout the house.
- Cracks appearing in drywall, door frames that suddenly stick, or new hairline cracks in the slab itself.
The 20-minute meter test you can run yourself
Turn off every water-using fixture and appliance in the home, including ice makers and irrigation. Find your water meter (usually in a pit near the street or in the basement near the main shutoff) and note the reading or the position of the low-flow indicator. Wait 20 to 30 minutes without using any water and read it again.
If the reading moved, you have an active leak. To narrow it down, close the main shutoff valve to the house and repeat. If the meter stops, the leak is inside your home's plumbing, often under the slab. If the meter keeps moving with the house valve closed, the leak is in the service line between the meter and the house.
How a plumber confirms and locates it
Guesswork is expensive when concrete is involved, so a proper diagnosis uses electronic tools rather than a jackhammer. A leak that goes unnoticed can quietly run up your water bill for months before any visible damage appears, and catching it early with non-invasive leak detection equipment saves thousands in repair costs later.
We isolate the hot and cold sides with a pressure test to determine which system is losing water, then use acoustic listening equipment to hear the escaping water through the slab and a thermal camera to trace hot-line leaks by temperature signature. That combination usually pins the break to within a foot or so.
From there you have real options: a spot repair through a small opening in the slab, rerouting the affected line overhead through the attic or walls, or repiping the section entirely if the pipe has widespread corrosion. Because clay soils behave the same way south of town, homeowners in Loveland see the same failure pattern in homes of a similar age.
What it costs to wait
A slab leak does not stay the same size. Water escaping under pressure erodes the soil supporting your foundation, and saturated ground under one part of a slab while the rest stays dry is exactly what causes differential settlement and structural cracking. Add continuous moisture under flooring and you get mold within weeks.
Most homeowners insurance covers the resulting water damage but not the pipe repair itself, and coverage often depends on acting promptly once you noticed the symptoms. If your meter test says water is moving, treat it as urgent and get a licensed local plumbing team out to confirm the source before the damage spreads.
Frequently Asked Questions
Can a slab leak fix itself?
No. Pinhole corrosion and cracked lines only get larger under constant water pressure. A leak that seems to come and go is usually a line that only leaks when a particular fixture pressurizes it.
How much does slab leak repair cost in Fort Collins?
Cost depends on whether we do a spot repair through the slab or reroute the line. We locate the leak first with acoustic and thermal equipment, then give a flat-rate quote before any concrete is opened.
Does homeowners insurance cover a slab leak?
Most Colorado policies cover the water damage caused by the leak and the cost of accessing the pipe, but not the pipe repair itself. Photograph everything and report it as soon as you suspect a problem.
Need a licensed plumber in Fort Collins?
Fix Plumbing Fort Collins is available 24/7 with flat-rate quotes and same-day service across Fort Collins and Northern Colorado.