Choosing Your Pipe: 8 Pipes to Consider for Your Trenchless Projects
The choice of pipe material has a lasting affect on any trenchless project. Be sure you use the right kind of pipe for your projects, and learn about the different types.
It’s hard to believe now, but the first commercial water piping was made using bored-out white pine timbers. The system was surprisingly water tight because water caused the wood to swell, thus sealing the joints. However, over the years a wide variety of piping materials have become available, each with their own advantages and disadvantages.
The choice of piping material often comes down to the lowest life cycle costs. But, this can vary depending on the trenchless method, the service of the piping, whether it is pressurized or not and its longevity in the specific ground conditions.
Here's a list of common piping materials and their features.
Concrete is a popular material choice for underground piping due primarily to its impressive strength characteristics. Its compressive strength usually measures in the range 4,000 to 8,000 psi. This makes it an ideal choice for pipe jacking and microtunneling where pipes are subjected to high forces.
Concrete piping also maintains its shape and wall smoothness over time. This gives it an advantage over other pipes because it has a consistent hydraulic performance. Deterioration in wall smoothness or pipe shape affect liquid flow and therefore pipe capacity.
Other advantages are the ability to create custom shapes for culvert sections or where there is a clearance limit.
Like concrete, ductile iron also has impressive strength characteristics. But unlike concrete, this strength is both compressive and tensile. This offers great advantages for trenchless methods where pullback is required. In addition, ductile iron distributes thrust or pulling forces around the pipe circumference.
Another benefit of ductile iron is that it can be detected from above ground using locators. This makes it easy to identify the piping route underground without excessive digging.
Vitrified clay is a ceramic material with exceptional characteristics for specific applications. It has an extremely high compressive strength of about 18,000 psi. It is therefore suited for pilot tube microtunneling, slurry microtunneling, pipe bursting and sliplining casing.
The high strength also means that vitrified clay piping does not need a surrounding of granular materials. This saves time and money in the installation as well as reducing the costs for soil removal as the bore size is kept to a minimum.
Vitrified clay is completely impervious to chemical attack. Its longevity means that the total life cycle cost for vitrified clay piping is very attractive. (To learn more, see The History of Vitrified Clay Pipe in Trenchless Installation.)
High Density Polyethylene
HDPE is a newer generation piping material, which has made great inroads into the market. A sewer pipe survey in the United States shows that for municipalities that restrict their piping materials to certain types, 61 percent of these municipalities have HDPE on their approved list. In particular, HDPE is the most used pipe material by municipalities for trenchless projects.
Some advantages of HDPE are its strength and flexibility characteristics. It has good liquid flow properties due to its smooth walls and it is resistant to pressure surges like water hammer. HDPE pipes come in very long lengths (especially smaller diameter pipes) causing a reduction in cost of joins. In addition, the flexibility allows for a bending radius up to 25 times the outer diameter of the pipe.
HDPE pipes are suitable for HDD, pipe bursting, sliplining and other trenchless applications.
PVC is another very popular new generation piping material. In the same survey mentioned above, 90 percent of municipalities responded as using PVC in their sewer networks. The same number of respondents indicated that this is their most commonly used material. Municipalities report that PVC pipes are the easiest to maintain and have the longest life cycle. Key features of PVC pipes are its longevity, durability, low maintenance and ease of assembly. Properly installed PVC pipes can last for over 100 years.
Fiberglass pipes are engineered for specific applications. Their thickness, strength and joint method can be designed to meet the project requirements. Fiberglass resists all forms of corrosive or chemical attack from inside or from soil conditions. An advantage of fiberglass pipes is their ability to withstand extreme cold.
Fiberglass piping is suitable for sliplining, microtunneling, directional drilling, pipe jacking, pipe bursting, tunnel linings and casings.
Whereas standard concrete pipes use cement and water as a binder, polymer concrete uses a high-strength, corrosion-resistant, thermosetting resin. This product was developed for the highly corrosive environment of wastewater systems. It is superior to concrete in these applications due to the uniformity of the corrosive barrier throughout the wall thickness. Even if the pipe is chipped or damaged, its corrosion-resistant properties remain intact.
Polymer concrete pipes are suitable for microtunneling, pipe jacking, one-pass tunnel segments and structures or shafts.
Steel piping first emerged in the 1850s and it has remained a widely used underground pipe because of its properties. It retains its properties indefinitely, compared to some plastic products which do lose their strength over time. Steel pipes are widely used in high-pressure applications and with hazardous materials like hydrocarbons due to its strength and ability to withstand internal pressure spikes.
Steel pipes can be used for directional drilling, jack-and-bore as well as pipe ramming projects. (For a comparison of material lifespans, see The Lifespan of Steel, Clay, Plastic & Composite Pipes.)
What We've Learned
Underground piping has come a long way from the hollowed-out pine logs of history. A wide range of materials is now available with research and development continuously improving the properties and features of piping systems.
Always buy certified piping so that you can be sure it meets the specifications for your project and inquire from your supplier if you are unsure about the type of material for your application.