Construction, overhead traffic and the changing structure of the earth itself all take a heavy toll on the pipes we depend on to deliver water and take away sewage. There are repair methods, such as sliplining, that offer extensions to a pipe’s life, but eventually, pipes crack. Eventually, they break up so thoroughly that they discharge more of their cargo into the soil than they deliver to its proper destination.

When this occurs, trenchless technology offers a solution in the form of pipe bursting performed by hydraulic – called static pipe bursting – or pneumatic pipe bursting equipment.

What Is Pipe Bursting?

Pipe bursting involves pulling or pushing a pipe bursting head – with a new pipe attached behind it – through an old pipe, bursting the old pipe and displacing its remnants into the surrounding soil. The old, existing pipe is not removed from the soil, nor is a trench required to install the new replacement pipe. Instead, the new pipe is pulled into place by the same pipe bursting head that breaks up the old pipe and drives it into the soil.

Not only is there no need for a trench, but the time required for replacement is also minimized. (Want to learn more about the basics of pipe bursting? Then check out An Introduction to Pipe Bursting.)

So, What Exactly Is Pneumatic Pipe Bursting?

Pneumatic pipe bursting uses a constant-pressure, air-powered winch to pull the pipe bursting head and the new pipe through the pathway, starting from an entry pit, going to a manhole. It’s used primarily for sewer line replacement. This method is powered by an air compressor and pulls the replacement line through the line to be burst. It’s the most common method of pipe bursting, being used in approximately 80 percent of pipe bursting jobs.

And What Is Hydraulic Pipe Bursting?

Hydraulic pipe bursting is similar to pipe ramming and uses the same technique to replace both waterline and sewer lines. Entry and exit pits are dug, the existing pipe disconnected at both ends, and a hydraulic ramming station is lowered into the entry pit (which includes space to lower the new joints of pipe into position ahead of the ram, in addition to the space required for the ramming station).

The new pipe is then hydraulically rammed through the old existing pipe. The pipe bursting head is removed at the exit pit. The pipe is then reconnected as required. Hydraulic pipe bursting is only used in approximately 20 percent of pipe bursting jobs.

What's the Difference Between Static and Pneumatic Pipe Bursting?

The unfavorable contrast between hydraulic and pneumatic pipe bursting machinery is small, and, generally, anecdotal and often revolves around the amount of noise any pneumatic process makes. Hard experience suggests that both can be maintenance nightmares, but hydraulic machinery uses hydraulic oil under pressure.

A pinhole leak in the hydraulic hose or larger leak in the hydraulic holding tank offers the opportunity for massive environmental damage. Pneumatic machinery is louder, but it's air-driven: A pinhole leak in an airline or a huge hole in the pneumatic accumulator won't cover Mother Earth with environmentally unfriendly oil.

What Are the Similarities in the Two Processes?

The biggest similarity between static/hydraulic pipe bursting and pneumatic pipe bursting lies in the pipe bursting heads used by both pneumatic and hydraulic pipe bursting. The pipe bursting head comes in two forms: the front mount and rear mount. “Mount” refers to the way the leading edge of the new pipe is mounted to the pipe bursting head.

The front mount pipe bursting head may be used with or without a pilot. It’s slightly smaller than the pipe it pulls into place. It eliminates the need for a receiving pit because it is towed (by the hydraulic winch) between two manholes, a distance of about 1,400 feet and the practical limit of a single pipe bursting effort.

When used with the pilot, the pilot reduces the tendency of the pipe to plow away from the specific path it should be following, which can occur when there are fractures in the old pipe that may cause the path of the new pipe to deviate significantly. A pilot is required for pipe bursting jobs involving cast-iron pipe.

The rear mount pipe bursting head requires a pilot. The bursting head is larger than the new pipe it’s pulling through the older pipe. The rear mount pipe bursting head is recommended when the old pipe must be displaced in compacted soil and when the new pipe is several sizes larger than the old pipe. (To learn more about other types of trenchless methods, see 7 Types of Trenchless Rehabilitation Methods and How They Are Used.)

While pneumatic or hydraulic pipe bursting may sound like the ultimate solution to broken subterranean pipes, that’s not always the case. Not all broken underground pipes can be rehabilitated in this way. Steel and stainless-steel piping are poor candidates for pipe bursting.

Although ductile iron can be replaced by pipe bursting, it’s a better candidate for pipe splitting, a similar process. Pipes over 42 inches in diameter are not candidates for pipe bursting because of their size.