How to Know if You Have a Slab Leak? Signs to Watch Out For

Slab leaks can seem like a minor inconvenience, but they can be huge, hidden problems beneath concrete slabs in homes and businesses.

These pesky leaks can cause serious damages, including water-related losses such as mold, damage to walls and carpets, shifting in foundations, and even damaged roads outside if the slab leak is large enough!

The best way to detect a slab leak before it causes major damage is to look for signs of increased water bills, wet spots on the floor or carpets, or warm spots near a water line. Slab leaks can also create a loud, rushing sound or vibration when the water is turned on.

how to know if you have a slab leak

What is a Slab Leak?

A slab leak is a plumbing nightmare. Water can seep in unnoticed and cause major damage to whatever structure the slab is supporting.

Before this insidious problem reaches its disastrous conclusion, it’s important to be aware of what slabs are and the signs that you may have a slab leak.

Often, it happens when a water pipe or connection to the wastewater system has failed under a foundation slab.

The occurrence of a slab leak is usually accompanied by bad news, mainly when it is not detected on time since it can generate multiple problems, such as weakening the foundation of your home.

When you’ve noticed these signs, expect that you’ll face a full-blown catastrophe one way or another. With that being said, knowing how to identify a slab leak is essential for preventing these disastrous outcomes.

The majority of slab leaks originate from corroded pipes, poor workmanship, or inferior materials. Its symptoms can also occur whether from below-ground water lines or above-ground plumbing fixtures.

For example, if you begin to notice warmer floors or moisture building up over your head, it could be a sign of an impending slab leak. If you hear whistling or rushing noises coming from beneath your floors, that’s another common symptom.

Most of the time, when we find out about slab on grade leaks, they have already caused significant damage. They tend to become very difficult to detect and repair. In this blog, we will answer these questions:

  • What are the common causes of slab leaks?
  • How to properly identify slab leaks?
  • What are some ways to repair the slab leak?

What Can Cause Slab Leak?

A leak is a sign of deterioration in the water supply system, poor connection in the sewage system, or loss of impermeability in the lining/cladding of the walls and floors around showers.

Here are some of the common reasons why slab leaks occur:

The Water Supply System Deteriorates

Under-slab leaks occur when a water pipe under a foundation slab fails. The failure can be caused by:

The environment in which the pipes are located, such as:

  • The incompatibility between the copper pipe and the type of soil (its resistivity, its pH, and its sulfur content), since this may contain something that causes a negative chemical reaction when it comes into contact with the copper pipes. This reaction is known as electrolysis, and it will happen at any time, even years after installation.
  • Longitudinal stresses are produced by thermal contractions and stresses caused by frost (low temperatures).
  • Differential movements of the ground.
house wall near the window with some water stain show peeling paint

The characteristics of the pipeline itself, such as:

  • The mechanical properties of the materials.
  • Dielectric permittivity.
  • The geometry of the pipes.
  • Material defect due to manufacturing.
  • Thickness and diameter.
  • Amount of material lost due to corrosion, and
  • size and distribution of corrosion marks.

The failure modes for these characterizations are usually longitudinal perforations and cracks.

To operational factors such as:

  • Bending stresses on the pipes due to faulty installation (trench and support bed) and other interferences such as accidental breaks.
  • The water pressure inside the pipe.
  • Loads of the ground, traffic, and compression force exerted by frozen water of the ground on the pipe.

Explosive breaks are generally the product of internal pressure and corrosion, while holes in pipes tend to be caused by corrosion.

In PVC plastic pipes (polyvinyl chloride), they tend to have joint failures due to the loss of property of the glue in pipes that conduct hot water.

Connection Defect in the Wastewater System Itself

Bathrooms usually have what we call permanent humidity. This condition can cause the formation of molds and bacteria due to the high humidity levels, especially in places with very low temperatures.

Underwater leaks occur when the sewage pipe under a foundation slab has a connection defect in the toilets/drains, particularly in the connection between the pipe and the sink trap.

Loss of Waterproofing

Slab leaks can also be caused by the loss of impermeability in the lining/cladding of walls and floors around showers. This is due to a lack of maintenance or an inferior product installed that has degraded over time.

While the majority of people believe that ceramic tiles are waterproof, this is only partially true. Ceramic tiles are not resistant to water and can absorb small amounts of moisture over time, causing the underlying grout or mortar to deteriorate and eventually compromise the waterproofing membrane beneath it. This allows water to enter the slab and cause a leak.

The loss of impermeability in the ceramic or similar lining/coating results in moisture damage to the structure that can be solved by placing adequate waterproofing.

How To Identify The Slab Leak?

Any leak may give out some sort of signal, and they may appear depending on how long it has been leaking and how large of an area it affects. Some leaks are easier to detect than others. If a slab leak is suspected, it’s important to have an inspection as soon as possible.

Signs to Watch Out for to Identify Slab Leaks

  • Check the taps and appliances that use water on your property for leaks.
  • Look for some mold/mildew accompanied by its characteristic odor.
  • Check if there is a considerable increase in your water bill.
  • Look for puddles of water, damp carpets, or warped wooden floors.
  • Check if the water installations become less potent.
  • Touch the ground for hot spots.
  • Check if the water heater is always on.
  • Look for cracks in the foundation that indicate a sewer leak.
Adhesive bandage holding together a splitting concrete wall. (Concept: termporary solution) Tight/shallow DOF on bandage.

We suggest you always stay alert. Try to keep your appliances airtight, and don’t stop paying attention to your water bill. Only then, in case of an unexpected increase, will you be able to identify a slab leak and address it as soon as possible.

If you have a cat, take advantage of it. Check the areas where your cat usually stays and sleeps. Cats often look for warm places to snuggle, and their favorite place may be directly over a hot water leak. Touching the ground and looking for hot spots can help you identify slab leaks.

Check for Water Leaks

In general, the water that reaches your property goes through a meter and a set of faucets. Depending on the condition of the pipes and their components, some leaks can be detected through these devices.

Here is a short list of how to check for water leaks:

  • Look for the house’s water meter. This is usually located on the sidewalk or within the garden that surrounds the house. If the meter cannot be found, call your local public facility office for information on where it is located.
  • Find the main water shutoff valve. In cold climate regions, the valve is usually located inside the house in places like the basement or garage. In hot climate regions, the valve can be on the pipe near the water meter or on the same pipe next to the house.
  • Turn off the taps and turn off any appliances that use water. Make sure that appliances that use water, such as the washing machine and dishwasher, are not on because if one remains on, it will be difficult to identify the leak. Turn off all the taps in the house so that you can detect signs of a water leak in the water meter.
  • Check for activity on the water meter. Using safety gloves, remove the cap from the water meter. Depending on the make and model, each has a method for monitoring water use. It can be the clock-like hands covering the meter, a leak gauge like a small triangle, or an odometer-like digital counter. With taps closed and appliances turned off, check for plumbing leaks by looking at the meter. Is there considerable movement in hand for the first few minutes? Is your leak indicator constantly rotating? Is your odometer counter moving? If any of these occur, you may have a plumbing leak.
  • Close the water flow to the house. If there are two valves, close the one closest to the house and don’t move the connected valve on the street side. Open a faucet away from the water valve to make sure the water flow is closed. Repeat the previous step. The meter should show the same behavior.

How To Repair The Slab Leak?

Although some plumbers offer free screening services, others can charge up to $ 400. If you suspect that you may have a leak in your home or property, we suggest you do one of the following as soon as possible:

Call a local water leak detection company online immediately before it is too late; make sure he’s a pipe repair specialist.

We suggest that before committing to a plumbing company:

  • Call other plumbing companies and ask for repair estimates.
  • Simply discuss the problem as it was described to you.
  • Once you have several written estimates, choose a plumbing company that seems reliable and offers its services at a reasonable price.
  • Verify that they have certified, legally operating plumbers with good online user reviews and that you mention leak detection or repair directly on your website, indicating that you have experience.
  • Verify that they offer a guarantee of their work and have immediate attention.
  • Expect to pay about $ 65 per hour or a fixed price based on the specific job.
  • Keep in mind that contractors who charge by the hour may be cheaper for minor repairs but can cost significantly more if the plumber encounters unexpected problems.
  • If you can’t find good plumbers online, ask friends, family, and neighbors for personal recommendations.

Additionally, check your homeowner’s insurance policy; some cover the cost of essential plumbing repairs. Plumbers may use special equipment to confirm and locate the leak.

From there, they’ll be able to isolate any problems, identify the cause and determine how to repair it. Depending on the size of your slab leak, repairs can range from simple patching or injecting epoxy, to replacing entire sections of pipe.

The cost will depend on the complexity of the repair work, as well as any additional equipment required. Regular maintenance and inspection are a great way to avoid costly repairs in the long run.

Photo of a Young Male Plumber with Protective Helmet who is Repairing a Water Pipe at the Construction Site.

How to Know if You Have a Slab Leak?

Remember, the majority of slab leaks can only be repaired by breaking the concrete.

While some of them may require only a small amount of concrete to be broken and replaced, others may require more extensive repairs. With that being said, look for a general contractor, or one that specializes in pipe repair.

Many of these companies offer free inspections and can also help you determine if a slab leak is the source of your problem.

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