How Can You Tell if You Have a Slab Leak?

Believe it or not, a true slab leak usually does not appear inside the home or cause damage to the interior of your house. In fact, it’s probably rare that a slab leak makes it to the floor or interior surface before you know that something is not right.

Given an extended period of time and complete saturation, water will eventually migrate into the interior of the home. Different soil types (clay vs. sand) and concrete footer depths can affect the problem. Or it may arise when the water has no place to go but through the path of least resistance.

The obvious signs of a leak are water coming up through your floor, from a wall, or under a cabinet. But there are other, more common signs and symptoms that might help you identify the possibility of a slab leak or some other kind of structural leak. Those include:

• High Usage Utility Notice: If your normal water usage jumps considerably, you will likely get a notice on your door or in the mail. This notice has a fairly low threshold, so it could be something as simple as a leaking toilet. No need to hit the panic button just yet.
• Water Bill: If you have no “high usage notice,” but your normal water bill jumps up considerably, this is a warning sign. Sometimes higher water bills are the first sign. We’re not talking about $50 to $100 higher but more like $300 to $800 higher than the previous 2-3 month average. Factor in seasonal changes for irrigation and pools before hitting the panic button.
• Hot Spot on Floor: Most slab leaks (70%) occur on the hot side water lines. An unusual hot spot radiating through the floor that was not there before is a telling sign. This is more noticeable in the colder months and on tile and wood floors versus carpet. Oddly enough, pets seem to congregate and lay on these spots, which can confuse matters—unless the entire room feels like a sauna.
• Running Water Sounds: Listen out for faint sounds of running water, hissing, or spraying when no fixtures are being used. This is usually more noticeable in the evening as things quiet down. Usually, these sounds can be heard in the walls behind tubs & showers but also under cabinets through the shutoff valves. If you have a tankless water heater and/or a hot water recirculation system, be aware that these sounds could be the system working during its programmed times.
• Water Meter Dial: If your water meter is registering usage but you aren’t using any fixtures, this could be a sign of a slab leak. If your water meter’s dial is spinning or the digital meter is counting up, do not be overly alarmed. The meter could be registering other leak-related items that are far simpler to repair, such as leaking toilets, irrigation, or your pressure-reducing valve (PRV).
• Flooring Damage & Differences: Wood flooring boards will start to swell and/or lift up, becoming uneven and exposing the sharp edges. You will also see cupping and peaking as the wood boards expand with moisture absorption. Tile floors might be damp, water may start puddling, and/or the grout will be darker than normal.
• Exterior Observations: Another fairly obvious sign is standing water or muddy spots, usually near the edge of the home or in low spots of the yard that never seem to dry. Sometimes, the leak will progress to the point where visible water might wick over the edge of the slab directly under the bottom row of bricks.