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Leak Detection

Slab Leak or Sinkhole? How to Tell the Difference Before You Call Anyone

A cracked wall and a damp floor can point to a slab leak or to something underneath the slab. In sinkhole country the difference determines whether you call a plumber or your carrier, and calling in the wrong order costs you.

By Justin Thurow August 24, 2026 · 7 min read

Pasco, Hernando, and Hillsborough County report more confirmed sinkholes than anywhere else in Florida. The same limestone that feeds the springs at Weeki Wachee also opens holes under whole neighborhoods. That rock creates a problem specific to this part of the state, because the early signs of a sinkhole and the signs of a slab leak look the same to a homeowner standing in their own living room.

A slab leak and an early sinkhole announce themselves the same way. A hairline crack appears in drywall or in floor tile. An interior door that closed properly for years begins to stick. A section of floor feels damp or reads warm underfoot. A water bill climbs without explanation. Every one of those symptoms appears on a slab leak checklist, and every one of them also shows up when the ground below starts to move. Telling them apart from the surface alone is not realistic, which is why the sequence of calls matters.

The practical difference between a slab leak and a sinkhole is where the water comes from. A slab leak is pressurized water escaping a supply line beneath the concrete, and it originates inside your plumbing system. Ground movement is soil and limestone shifting under the foundation, and the water involved is groundwater rather than yours. That distinction has a convenient consequence. A slab leak consumes metered water and a sinkhole does not, which makes the water meter the fastest and cheapest test available to a homeowner.

Run the water meter test before you call anyone. Shut off every fixture and appliance in the house, including the ice maker and the irrigation system, then observe the meter for roughly fifteen minutes. Movement confirms that water is leaving your system somewhere, which points strongly toward a plumbing failure. A meter that sits perfectly still while cracks continue to widen points away from plumbing and toward the ground beneath the structure. Neither result is certain by itself, but the difference determines who you should be calling.

The pattern of the cracking separates the two as well. Slab leak damage usually stays in one spot. The damage concentrates near the leak, in one room or along one wall, and the wet area lines up with a plumbing run. Ground movement tends to be wider and more structural. Cracks appear on multiple walls or on opposite sides of the house, exterior stucco separates, window and door frames rack out of square, and in some cases the ground outside shows a depression or a circular slump that was not there the previous season.

The order in which you make those calls matters more than most homeowners realize. If the meter is moving, start with a plumber, because a confirmed and repaired slab leak may fix the whole problem at a fraction of the cost of soil testing. If the meter is still and the structural symptoms are broad, contact your insurance carrier before hiring anyone. Florida Statute 627.7073 governs the testing an insurer may require, and carriers usually prefer to direct that soil testing themselves rather than pay back one you ordered on your own.

Two points of honesty are worth stating plainly. Standard Florida homeowners policies do not include sinkhole coverage at all. They include catastrophic ground cover collapse, which is a much narrower clause that requires the home to be condemned. Broader sinkhole coverage is a separate endorsement you had to purchase, and many homeowners in this area assume they carry it when they do not. Check the declarations page before you assume a result, and note that Florida Statute 627.706 bars a sinkhole claim filed more than two years after you knew or should have known about the loss. The second point is that we are plumbers rather than geologists, and we will say so.

What Farrell Plumbing can do is settle the plumbing question quickly and for certain. We run a meter isolation test, pressure test the supply system, and locate any active leak using acoustic and thermal equipment before anything is opened. If we find a slab leak, we repair or reroute it and you have your answer. If the system holds pressure and the meter is still, we document that result in writing, which is exactly the evidence your carrier will want before paying for soil testing. We hold Florida license CFC1430362 and work throughout Pasco and Hernando County.

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FAQs

Common questions on this topic.

Quick answers from our expert plumbers. Still have a question? Call our team and a real person will pick up.

01 How can I tell a slab leak from a sinkhole?
Start with the water meter. Shut off every fixture and appliance and watch the meter for fifteen minutes. A slab leak consumes metered water and will move the dial. Subsidence involves groundwater rather than yours and will not. Slab leak damage also tends to be localized to one area, while subsidence produces broader structural cracking.
02 Does homeowners insurance cover sinkholes in Florida?
Not by default. Standard policies include catastrophic ground cover collapse, which requires the structure to be condemned and is much narrower than most homeowners assume. Broader sinkhole coverage is a separate endorsement that must be purchased. Check your declarations page before assuming you are covered.
03 Should I call a plumber or my insurance company first?
If the meter is moving, call a plumber first. A repaired slab leak may resolve the problem entirely at a fraction of the cost. If the meter is still and cracking is widespread, contact your carrier before hiring anyone, because insurers generally want to direct the geotechnical testing themselves.
04 Why are sinkholes so common in Pasco and Hernando County?
The limestone bedrock underlying this part of Florida dissolves as groundwater moves through it, creating cavities beneath the surface. The same geology that produces the springs in this region produces subsidence under residential neighborhoods, and these counties report among the highest confirmed sinkhole counts in the state.
05 How long do I have to file a sinkhole claim in Florida?
Florida Statute 627.706 bars a sinkhole claim, including supplemental and reopened claims, unless you notify the insurer within two years of when you knew or reasonably should have known about the loss. The clock runs from discovery rather than from the date the damage began.
06 How do I test for a slab leak myself?
Shut off every fixture and appliance that uses water, including the ice maker and the irrigation system, then watch the water meter for about fifteen minutes. Any movement means water is leaving your system somewhere. A still meter alongside widening cracks points away from plumbing and toward the ground under the house.
07 Who should I call about foundation cracks and a damp floor in Spring Hill?
Start with the water meter test. If the meter moves, call a licensed plumber first, because a repaired slab leak may resolve the whole problem. Farrell Plumbing, license CFC1430362, performs meter isolation and pressure testing across Pasco and Hernando County and documents a negative result in writing for your carrier.

Have a more specific question? Contact our team or give us a call.

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