9 Warning Signs of a Slab Leak

Are there pools of water or bad smells in your home? Homeowner’s with slab-type foundations need to know the warning signs of a slab leak.  Detection and repair of slab leaks is essential to save money in further damages, while protecting the value of your home.

Using a slab for a house’s foundation is nothing new. Since the end of WWII, home builders have been using slabs to save time and money in construction. Contractors pour a half-a-foot of concrete onto a prepared surface with a water supply running underneath. Slab foundations are easier and cheaper than forming out an entire basement.

warning signs of a slab leak
A slab foundation for a new home in Las Vegas

What’s a Slab Leak

Slab leaks occur under the foundation (or slab) or your home. These types of foundations are used throughout the U.S, in places like Las Vegas were most houses don’t have basements.

Slab leaks are a serious problem for homeowners.

The challenges are obvious: the leak must first be detected and then repaired. Your floor might need to be excavated to access the leaking pipe. This is a costly inconvenience, as water mains are shut down on your home, flooring removed, and water lines are either repaired or replaced.

9 Warning Signs of a Slab Leak

1. Spike in the Water Bill

Have you noticed sudden increases in your water bill? Sudden increases of water use, with no real change in your regular water consumption can indicated a leak.

Pro Tip:

If you notice an increase in your water bill, check your sprinkler lines. Sometimes sprinkler line heads or valves go bad. Check also the heads on drip lines as these can loosen and pop off over time.

2. Notice from the Water Utility Company

Have you received a letter from the water district informing you of a leak?

If yes, then time is of the essence. Water districts place the responsibility on the homeowner to detect and repair the leak. Usually they offer little information or detail about the leak. All the water utility company knows is that your water usage is abnormal.

Don’t wait to act if you’re contacted by your water provider. Homeowner’s can be subject to fines if they don’t fix the leak.

receiving a notice - slab leak signs
“What’s this?  You didn’t fix that slab leak!?”

3. The Sound of Running Water

With all fixtures and faucets “off” do you hear water running? If yes, try to identify the source of the sound. Look around the area. Are there any other slab leak signs, such as damaged flooring, that might indicate a leak?

If you hear water running below the floor or in-between your walls, call a plumber immediately. Leaks can create extensive damage to other areas of your home.

4. Low Water Pressure

Has there been a loss of water pressure in your house? If you’re taking a shower and there is a change in water pressure this could be a sign of a leak. Check the faucets inside your home and verify if water pressure is low on multiple faucets. If it appears low in other rooms, you have a problem.

5. Warm Sports on Your Floor

Hot water lines go bad more often than cold water lines. The added temperature of a hot line puts pressure on joints and fittings and can lead to failure.

When a hot line breaks or leaks underneath the slab, you might experience warm areas on your floor. This will be more evident with wood or tile flooring.

6. Pools of Water or Damp Carpet

Are you finding wet spots on your floors or carpet? Moisture on your hardwood for example, or wet spots on the carpet are warning signs of a slab leak.

Check around the area. If the leak is near a wall, look at the bottom of the baseboard. Is there water running along its length? Are there any signs of water leakage from behind the wall or from above?

Speak with a licensed plumber to verify your findings. With a careful diagnostic, a plumber can rule-out other possible explanations and begin to detect the source of the leak.

7. Damaged Flooring

Is there damaged flooring in your house that wasn’t there before? This could be a sign that something underneath is creating moisture and damaging your floor. Undetected moisture from a slab leak can result in bulges or cracks in the flooring.

8. Bad Smells

The nose, knows.

Our sense of smell is one of the most powerful tools we have in understanding our environment. The smell of mold, mildew, or wet and damp smells are strong indicators that something is not right with your plumbing system.

9. Mold and Mildew Growth

The growth of mold or mildew is also a cause for concern. This indicates an active leak and probably one that has gone undetected for a long time.

Whenever you encounter mold, exercise extreme caution. Mold spores can cause allergic reactions and even make a person sick. Don’t disturb the area until a qualified professional can evaluate the source of the leak and provide a plan for remediation.

How to Tell if You have a Slab Leak

Run a Test

As a homeowner, you can perform a simple test to determine if you may have a leak.

  1. Turn off all water fixtures and outlets
  2. Locate your outside water meter
  3. Observe water meter for 2–5 minutes

Make sure all water outlets, fixtures and outside water is off. This includes all the fixtures your kitchens and baths that may run water.

Go to your outside water meter. Typically, these are near the street. If you are unsure, call your water utility company and ask for the location of the meter.

how to tell if you have a slab leak - run a test at your meter
Observe the water gauge for a few minutes to verify water usage.  Some meters used today are digital.

Your water gauge should include and arrow or gear that shows the water usage. Watch for any movement in the gauge. Spend a few minutes to watch the gauge to ensure that you’re getting a good reading.

If after a few minutes the gauge is still moving even though the water is turned off—inside and outside your home—this is a warning signs of a slab leak.

How Common are Slab Leaks?

It depends. Many factors can go in to creating a slab leak. These can include the following:

High Water Pressure

A water supply that provides constant high-pressure input to your home’s water system can impact pipes and joints. A water pressure test gauge can determine the pound-per-square-inch (PSI) of your supply line. A licensed plumber can do this to determine if this an issue for your home.

Changes to Soil Composition

Do you live in an area subject to earthquakes or flooding? These types of natural events can alter the soil structure underneath and around your home, creating breaks or bends in your supply lines.

Flooding can erode the soil. Shifting soils and erosion can create hollow spaces underneath your floor, resulting in cracks and further damage to your home’s foundation.

All this movement is not good for your plumbing system. Plumbing systems rely on the ground underneath for support, and to maintain consistent flow and performance.

Age of Your Home

Unfortunately, things get old and stop working the way they should. If you have and older home, you know this all-to-well.

Old pipes can give out from wear and tear. Years of use and the constant water pressure in the lines, can erode a plumbing system’s performance.

Is a Slab Leak Covered by Insurance?

Under most circumstances, the answer is “no.” If you live in an area prone to earthquakes or floods, and one of these events happens, your policy might offer some coverage. Homeowners in natural disaster zones are often required to carry extra insurance riders on their policies.

Check with your insurance company and find out what your policy covers.


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