DFW Foundation Repair and Construction not only specializes in foundation repair and concrete construction but we’re also experts in under slab plumbing repair and tunneling. When you have a leak from a broken water supply line or a large sewer line under your slab you have two options if you want to repair them.
One is to go through the slab with a jackhammer hoping to get as close to the leak as possible, oftentimes missing the mark by feet or worse yet discovering that the pipe has a hairline fracture or crack invisible to cameras that travel down the length of the pipe. This means that going through the floor was a waste of time because now you’re going to have to chase down the length of the pipe to find the leak to make the repair. The other option is to dig a tunnel under the slab from outside the house and chase down or follow the length of the pipe until you find the leak.
This technique is very labor-intensive and tedious but probably the best way to accurately locate the leak without damaging your slab floor and causing a big mess. Tunneling is the preferred method of under slab leak location and repair and a lot of the time it’s the only accurate way.
The way it’s done is very simple and straightforward. First, we dig a 4ft x 4ft 3-dimensional space outside the concrete perimeter beam of the house or commercial building and then we continue to dig under the beam until we find the pipe we’re looking for. Once the bad pipe is located, we methodically dig around said pipe while simultaneously enlarging the tunnel so that the deeper we go, the more men can fit into the shaft thus building a chain of men to move the material out from the back of the tunnel one man to the next until the dirt is displaced outside.
Extreme caution and care are needed when performing this type of dig because tunnels can and sometimes collapse or sometimes the men can collapse due to oxygen deprivation. If the tunnel is 50ft-100ft or more we’ll use fans or portable air conditioners with ducts to pump fresh oxygen down to the guys so that they can maintain their faculties. Some residential slab beams go down 1ft or 2ft or if it’s a commercial job then sometimes the beams go down 5ft-6ft or deeper.
Once we locate the area of the leak, we disassemble the pipe or pipes and replace the damaged one with a brand new PVC pipe. We then suspend the new pipe on metal hangers that we screw into the slab to prevent the slab from crushing the new pipe if there are ever any foundation issues. A lot of companies simply place the new pipe in the dirt directly under the slab and then when there’s foundation movement or settling, the new pipe gets crushed under the weight of the foundation.
The hangers prevent this from happening. After the repair is achieved we backfill the tunnel with the displaced dirt and soak it with water to achieve a certain amount of compaction and we continue doing that until all the dirt is back in the hole.
Sometimes we’re able to get most of the dirt back into the tunnel but oftentimes there’s a little bit left because when you dig out a tunnel, the dirt has been compacted and compressed for many years and when you displace it you aerate it which gives it volume thus making it difficult to get all the material back in. If it’s just a small amount we’ll spread it out over the yard evenly or else we’ll build a little angle of material against the house so that rainwater flows down the pitch away from the foundation. If the amount of material is significant, we’ll load it up in a trailer and drop it off at a site specifically used for dumping sand, dirt, or loam.
Either way, we handle it so you don’t have to. If you need tunneling for a plumbing repair or new plumbing construction in the DFW area please do not hesitate to contact us.