Most people are unfamiliar with the term ‘Trenchless Pipe Replacement’. Some other names commonly used are “No-Dig”, “trenchless pipe rehabilitation”, “pipe breaking”, “Trenchless Technology” and “trenchless pipeline replacement”. No matter which name it is going by it simply means splitting an old, worn out pipe while inserting a new one …all at the same time!
Trenchless technology includes a large family of methods utilized for installing and rehabilitating underground utility systems with minimal surface disruption. Basically it refers to a method of replacing underground pipe-work without digging long, ugly trenches that disrupt lawns, sidewalks, driveways and just about any other property feature that has the misfortune of existing above an underground line!
The trenchless method installs the new pipe by pulling it through the old pipe, even if the existing pipe is collapsed, behind a special breaking head (or cone) that expands a clear channel ahead of the new pipe as it travels underground. One small pit is all that is necessary for most jobs in order to feed the new pipe into the ground … a compact but powerful pulling machine is located at the destination point, often inside a building, to pull the pipe in from the pit.
The operation is simple, requiring relatively few steps.
The first step is to determine where the line must begin and then end. Once determined, two small pits are dug, each approximately 24″ wide x 36″ and as deep as required for the particular job. One pit (the entry pit) will be used to feed the line, and the other (the pulling pit) will contain the pulling unit ready to pull the pipe through the ground.
The pulling unit is then assembled in the pulling pit and butted against wooden shoring that surrounds the old pipe or newly bored pilot hole. Next the pulling cable is hand-pushed from the entry pit through to the pulling pit and threaded into the machine.
In the entry pit, the cable is passed through the hollow bursting cone, through the pipe guide, through the new pipe and attached to the pipe boot with a retaining pin. (See diagram)
Once assembled and ready to go, the Honda power pack is started up, charging the hydraulic cylinders, or on heavier jobs the backhoe is positioned and the chain attached. The pulling operation can now commence. The unit will pull the new pipe through the soil at a rate of approximately two feet per minute up to four feet per minute . (Note: Some soil conditions may cause this rate to vary).
In the entry pit, as the new pipe is almost all the way in, the process will pause. The cable will be fed through the next length
of pipe, the boot and pin attached, and the head of the new length will be fused to the tail of the preceding one. The pulling process can now resume and the cycle will be repeated until the job is finished.
Once done, the pulling unit is disassembled, the cable is retrieved and the pulling process is complete. The diagram below illustrates the process the process overall.
*Please note that for the purposes of this brief description, “pipe” refers to the line being pulled no matter what type.