There can several causes of leaks below a concrete slab, the most common reason in DFW is the clay soil below your foundation. Clay expands when wet and shrinks when dry, and moisture levels are continually changing.
Heaving and settling soil below the slab puts unacceptable amounts of pressure on the concrete, causing the concrete to shift, heave and crack. Underground plumbing is connected to the slab in several places. When movement of the slab occurs, breaks in the pipes (both water-supply and waste-lines) can occur.
Al’s Plumbing repairs any type of slab leak in any location. Al’s does not cut through slabs, we tunnel under the home and do the work from below the slab. The slab remains unaltered and as it was designed and built to perform.
Homes built since around 1990 have a Post-Tension Slab. This type of slab cannot be cut due to safety risks and undermining the integrity of the slab if one of the cables inside the slab becomes severed.
How To Determine If You Have A Water-Supply Line Slab Leak
Did you suddenly have a spike in your water bill? If nothing in your consumption patterns has changed, you likely have a new slab leak
Use this simple test. With all water faucets in the house turned off, look a your water meter to see if it’s showing usage. If everything inside is turned off, the meter will not be showing usage.
If every faucet is turned off and you see usage on the meter, you have a water-supply line which is leaking.
Slab Leak Due To A Leaking Sewer Pipe
It is also possible that a waste line is leaking under the slab. This is harder to spot. If you have wet soil along some portion of the outside of your home when everything else is dry, you may have a waste-line (sewer) pipe leak.
Why would you suddenly have a waste-line leaking? The most likely cause is failed cast-iron sewer pipes under the slab. Cast-Iron pipes typically rust from the inside out, but also can rust from the outside due to contact with soil under your home.
A cast-iron sewer pipe which has failed do to rusting from the inside to the outside.
A cast-iron sewer pipe which has rusted from the outside. The area pointed out is where a hole has formed completely through the pipe.
Cast-iron pipes are also subject to breaking. They can break due to the pressure exerted on them by a foundation which is moving — in most cases due to our clay soil in DFW.
Waste-line leaks are as important of a problem as water-supply lines leaks. Any recurring moisture under the slab will form an increasingly large area where the clay soil has expanded and is pushing up on the slab from below.
Want to learn more about cast-iron pipes? More details on cast-iron pipes
When Were Cast-Iron Pipes Used?
Cast-iron (under slab) sewer pipes were installed in new homes until about the mid 1970’s. After that, PVC pipe replaced cast-iron in nearly all homes. PVC pipe does not have any rusting issues. There is another type of pipe (which is black) which and many similarities with PVC.