How much does it cost to repair a slab leak?

Reviewed by Adam Graham remodeling expert. Written by Fixr.com.

In many areas of the country, homes are built on slab foundations rather than full basements. In this case and depending on the location and how old your home is, you may have pipes running beneath that slab. Over time, soil expansion, corrosion, and other issues may cause one of these pipes to leak. If not timely fixed, this can lead to serious water damage inside your home and problems with your foundation and landscaping.

Slab leaks can be repaired using several methods, depending on the leak location and pipe type. The national average repair cost is $1,000 to $4,000, with most people paying around $2,500 for leak detection, tunneling repair, and foundation crack filling. This project’s low cost is $600 for leak detection and a small epoxy repair. The high cost is $15,000 for completely rerouting all pipes from under the slab to the home’s attic.

Cost to Repair Slab Leak

What Causes a Slab Leak?

A wide range of issues can cause slab leaks. Your location, soil type, age of the home and pipes, pipe material, and things like your water quality can all potentially cause a slab leak. In some cases, the cause of the leak may impact the repair type you have and its total cost. In other cases, the leak cause may be irrelevant to the repair. Below are the most common types of slab leaks.

Expansive Soils

Soil movement, expanding and contracting, can be a serious cause of leaks. Expansive soil is not present everywhere, but it is a contributing factor into why people build on a slab in the first place. Expansive soil can absorb water and expand, taking up more space. Basement walls may cave in if exposed to expansive soil, so slabs are the most common foundation in areas where this is an issue. The soil expanding and contracting over time can cause pressure beneath the slab, causing the slab or pipes to move and crack and resulting in leaks.

Excessive Pressure

Soil movement can cause pressure to build up under your slab. When this happens, a pipe may crack. Cracked pipes that are under pressure are usually found quickly because water may burst from them. This can cause significant issues beneath the slab, and water may even erupt into your home. If your leak is caused by pressure, take care of it immediately to prevent further damage.

Inappropriate Pipe Materials

Pipes can be made out of many different materials. Before the 1960s, galvanized steel and cast iron were two of the most common materials used beneath slabs. These materials and copper pipes may be impacted by soil, moisture, and water chemistry. This can cause the pipes to corrode or deteriorate over time. Because they are under the slab, you may not notice a small leak until it has expanded and becomes a problem.

Water Chemistry

Highly acidic water may interact badly with certain pipe materials. This is particularly true of galvanized steel and cast iron, but it may also be true of other materials like copper. This is why older pipes are more likely to be a problem over time because the acidity in the water may cause corrosion. Fixing this issue generally means replumbing the home or rerouting the water with new pipes that can withstand your water chemistry.

Slab Leak Detection Cost

If you suspect you have a slab leak, call for a slab leak detection test. Your plumber can carry this out by testing things like water pressure in the area, examining the slab for cracks and signs of moisture, and checking the surrounding landscaping for signs of excess water. This process costs from $100 to $400, depending on how invasive the detection needs to be. Some leaks can be spotted in minutes, while others take over an hour to be found and require the plumber to drill holes, clear soil away from your foundation, or insert cameras into drain lines to find the leak source.

There are many signs that a slab leak may be present in your home. If you detect any of the following issues, it is best to call in a plumber for a professional leak detection assessment to find out more.

Cracks in the Foundation

Concrete foundations can develop cracks for many reasons. However, any new or widening cracks should be checked by a professional. Water leaking beneath your slab can put pressure on the concrete. In turn, this can cause new cracks to form. Over time, this can translate into serious water damage, so always have new cracks checked in a timely way.

Bad Odor

If you notice a bad or musty odor coming from rooms on the slab, it can be a sign of a water leak. Musty odors may be caused by mold or mildew developing beneath your flooring over the slab. This may be particularly noticeable if you do not have a vapor barrier over the slab.

Mold

Mold growing on your walls or floors in the rooms just above the slab can be a sign of a water leak. As moisture increases under the slab, it will begin to seep through the slab. From here, it may be easily absorbed into the flooring or drywall. Water spots and soggy areas accompanied by mold may be a sign that you have a slab leak.

High Water Bills

If your pipes are leaking, you will use more water than usual. If your water usage is not increasing but your water bill is, it is a good indication of a leak. If this high water usage continues or rises, get a leak assessment to find out where it is coming from.

Low Water Pressure

As water begins running out of the pipes beneath your slab, you may notice a drop in water pressure everywhere else. A closed pipe system will have consistent pressure throughout. When you open that system and bleed off water, you also bleed off pressure. Low water pressure combined with a higher water bill is usually a sign of a water leak.

Sound of Running Water

If no faucet or shower is running in your home, but it sounds as though there is, this can be a sign of a leak. If you are standing above the slab, you may be able to hear water running. This is more prominent when the leak is larger. It may be difficult to hear smaller leaks.

Flooding or Puddles in the Lawn

The water leaking under your slab has to go somewhere, and the most likely place is into your landscaping. You may notice puddles or flooding in the yard. You may also notice that your grass or the shrubs near your foundation look lush and green and that they are growing faster than the plants in other parts of your yard.

Slab Leak Repair Cost by Type of Repair

There are many ways to repair a slab leak. Some methods may be specific to the type of pipe or leak. Others may be a better fit for certain soil conditions or the leak’s location along the pipe. In some cases, a plumber may give you options, while in others, there may be just one choice that will solve the issue permanently. The cost of each project varies depending on the pipe type, slab thickness, soil, and leak size.

Concrete Slab Sealer

The cost to seal your concrete slab is $100 to $200. Concrete sealing may need to be done after you take care of any leaks. Because concrete is porous, it can absorb moisture and water, which can lead to issues such as efflorescence, cracking, and mold. By sealing your concrete, you help prevent it from absorbing moisture and impacting the flooring you install over it. An alternative to sealing your concrete before installing new flooring is to put a vapor barrier down.

Repair a Broken Pipe Under a Slab

The cost to repair a broken pipe under a slab averages $200 to $2,000. The cost range depends on several factors. The pipe type and extent of the damage are the biggest determining issues. Some pipes can be easily repaired with a small amount of epoxy, which is the least expensive repair type. Others may need to have a section of the pipe completely replaced to make the repair. These costs are only for the repair. To make the repair, you need to be able to reach it, which can be done through tunneling, opening the concrete slab, or through readymade openings designed for this purpose.

Patching a Concrete Slab

The cost to patch your concrete slab ranges from $250 to $800. Patching may need to be done for several reasons. If you had a small cut made in the concrete to access a pipe, it needs to be patched. In many cases, leaks beneath your slab may cause cracks in the concrete to form. Existing cracks in your concrete may also widen with moisture. Patching these cracks can help your slab maintain its integrity.

Pipe Lining

The cost to line a pipe to help prevent future leaks is $500 to $2,000. The pipe length largely determines the project cost. Trenchless pipe repair or trenchless pipe lining is one of the least invasive ways to fix a leak. It is priced by the linear foot, so the longer the pipe, the higher your costs. This repair is not always an option for pipes under a slab. But when it can be done, it can save you money on the total job cost.

Breaking a Concrete Slab

The cost to break a concrete slab averages $500 to $3,000. Breaking the slab is one method of reaching the pipes. If you cannot do a trenchless sleeve and it is not possible to tunnel under your home, slab breaking is usually the answer. How much of the slab must be broken depends on the leak size. If you have flooring on your concrete, this must be removed first. Sometimes, the flooring can be saved and reinstalled. With this method, you frequently need to replace the flooring after the pipe has been repaired and the concrete patched.

Tunnels Under a House

Tunneling under the house ranges from $900 to $2,000. Tunneling involves digging in the soil under the home, draining it of any moisture, and then making the repairs to the pipe. This is a good option for anyone with expensive flooring who does not want to remove it. This can only be done in areas where the soil is stable enough to support it. Homes with shifting or expansive soil may not be good candidates for this repair type. Once the repair is made, the tunnel is filled back in, making this one of the least invasive processes for the homeowner.

Rerouting Plumbing Lines in a Slab Foundation

The cost of rerouting plumbing lines from a slab foundation is $4,000 to $15,000. Rerouting is often the answer when you have more than one pipe issue under the slab. Instead of repairing the pipes, the pipes are capped off, and new pipes are installed to carry the water. Instead of continuing to run beneath the soil, the pipes are usually rerouted through the attic. If you have expansive soil and significant moisture issues, rerouting your pipes can give you a permanent solution rather than a temporary one.

Slab Leak Repair Cost by Type of Replacement

When you have a slab leak, you often have more than just a few small issues to repair. If the water damage is extensive enough, you may need to replace a subfloor over the concrete, the concrete slab itself, or you may need to replace the pipes involved. Each of these issues has its own set of costs, in addition to things like inspection costs and possible repairs.

Replacing a Water-Damaged Subfloor

The cost to replace a water-damaged subfloor is $500 to $1,000. Sometimes, you may install a wood subfloor over your concrete slab before installing your main flooring. This is not always necessary, but it can be useful for some flooring types. If you have a slab leak, this subfloor will become waterlogged. At this point, it may warp or develop mold or mildew problems. If this happens, you need to replace it. This includes removing the old subfloor and making sure the area beneath it is completely dry before the new subfloor goes down.

Concrete Slab Replacement

The cost to replace your concrete slab ranges from $4,000 to $8,000. If you had to break up the slab to reach the pipes below, you may need a slab replacement. Sometimes, this means just replacing a section of the slab, while you may need to entirely replace it at other times. This depends largely on its condition and how much of the slab needs to be broken up to reach the pipes. If the slab has sunk or is severely cracked, you may need to completely replace it. If only a section needs to be broken up but the rest of the slab is in good condition, you may be able to salvage the rest to keep costs down.

Replace the Plumbing Under a Slab

The cost to replace the plumbing that runs under a slab averages $4,000 to $15,000. In general, if the plumbing located beneath the slab is compromised, the most common process is to replace it through rerouting. This means that instead of removing the old pipes and putting in new ones, which would include either needing to tunnel or replace your slab, the old pipes are left in place. They are capped off, and new pipes are installed that run through a different area. The most common place to locate the new pipes is in the attic, which is less invasive than installing new pipes under the slab.

Labor Costs to Repair a Leak in a Slab Foundation

Slab leaks are repaired by plumbers, who charge between $45 and $200 per hour. Most people typically pay between $75 and $130 an hour. Some jobs may be priced by the foot, including labor and material, while others have separate labor and material costs.

On average, you will pay between 1 and 3 hours for an inspection. The actual leak repair can take anywhere from 2 hours to 3 days, meaning your labor costs could be $90 to $4,800. In general, expect a minimum labor cost of around $150 to $200, plus the inspection cost for small jobs.

How Long Does It Take to Fix a Slab Leak?

It can take anywhere from a few hours to a few days to fix a slab leak. The time required depends on the leak size, location beneath the slab, materials, and repair method. Trenchless repairs are the fastest and can be done in a couple of hours. Tunneling may take 4 to 6 hours, while breaking up a slab and repairing the pipe below it may take 1 to 2 days. Rerouting your plumbing will take the longest time.

Does Homeowners Insurance Cover Slab Leaks?

In most cases, slab leaks are not covered by your homeowners insurance. This varies by policy and region, however. So if you suspect you may have a slab leak, call your insurance company first to find out what is covered. If it is covered, your insurance agent may outline what procedures are covered and may recommend a specific plumber. Trying to claim the repairs afterward usually results in a denial.

Additional Considerations and Costs

• Permit. Permits are not always necessary for this work. However, double-check with your municipality to find out more.
• Licensed professional. Always use a licensed plumber for this job. Slab repair is invasive and should always be carried out by a licensed professional who is fully insured.
• Insurance. Insurance does not normally cover slab leaks except in rare cases. Always check with your insurance agent.
• Danger. Slab leaks that go undetected for too long may cause serious erosion beneath your foundation. This could lead to issues that may endanger your home and family.
• DIY. Slab leaks should always be taken care of by a licensed plumber. Do not attempt to make these repairs DIY.
• Warranty. Some rerouting may come with a warranty on the pipes or installation. Repairs beneath the slab do not usually come with a warranty.