IRON KNIGHTS METAL WORKING

Choosing the Right Pipe for Underground Utility Applications

There are a number of conduit and innerduct options available for underground utilities applications. Choosing the right pipe can provide significant savings, both in material and labor costs. Below are several types of underground and electrical conduit, with the advantages and disadvantages of each, so you can make the best choice for your application.

HDPE Pipe

High density polyethylene or HDPE pipe is a strong, light weight and flexible product that can be used as conduit (duct) or innerduct. Both smooth and corrugated HDPE varieties are available.  HDPE is often used in electrical, utilities and telecommunications to protect underground cables and lines from impact, environment, weather, rodents, and other corrosive conditions.

Advantages:

• HDPE pipe easily bends around obstacles like roadways or rivers. This allows trenchless installation of underground lines and provides a significant cost savings.
• HDPE pipes are flexible and can be bent to a minimum bending radius of 30 times the pipe's outside diameter
• HDPE pipe joints can be heat fused together to form a leak-free and extremely strong joint.
• The flexibility of HDPE pipe makes it ideal for areas that are prone to earthquakes.
• Service life of HDPE pipe can be 50+ years, keeping replacement costs low.
• HDPE pipe is corrosion, abrasion and tuberculation resistant.
• More impact resistant than PVC pipe, especially in conditions with low temperatures.
• Lower cost and lighter weight than metal pipes.
• Available in longer lengths than pvc, allowing installation of longer lines with less jointing.

Disadvantages:

• HDPE pipe is shipped on rolls that may need to be returned to the manufacturer after use.
• Ovalizing of the pipe can occur from being wrapped on the rolls.

Rigid PVC Conduit / Bore-Gard

Rigid PVC Conduit, also known by the brand name Bore-Gard, is a flexible and strong product like HDPE pipe, but is cut and shipped in shorter, straight sections, rather than being wound on a roll. PVC conduit is also used in electrical, utilities and telecommunications to protect underground cables and lines.

Advantages:

• PVC conduit in straight sections is easier to handle than reeled conduit.
• Straight sections can be bundled and more can be shipped at one time than reeled conduit, providing a shipping cost savings.
• Straight sections of PVC conduit do not ovalize, but keep their shape, allowing greater internal fill capacity.
• Smaller sections allow PVC conduit to be carried over rougher terrain than reeled conduit.
• Strong and flexible for directional drilling installations, including multiple pipe bores.
• Joining is accomplished by hand, not requiring special fusion equipment.
• Rigid PVC pipe is corrosion, abrasion and tuberculation resistant.
• Accepts standard elbows and fittings.
• Available in 3-6 inch dia. 10 to 20 ft. lengths in sch.40 and sch. 80.

Disadvantages:

• Shorter lengths require more joints than with longer HDPE pipe.
• Less flexible than HDPE conduit.

Split PVC Conduit

Split PVC Conduit is impact and ultraviolet resistant interlocking conduit that snaps together to encase fiber optics and cables.  It is often used for repairing lines without having to cut the cables or connectors housed inside conduit.

Advantages:

• Impact and ultraviolet resistance makes split PVC ideal for fiber optics and cable installations.
• Allows for repairing of lines without cutting cables and connections, leading to significant cost savings.
• The snap-together design is fast and easy to install.
• Joints can be reinforced or sealed with plastic or metallic straps.

Disadvantages:

• Most split PVC conduit is not UL listed, and therefore is not recommended for electrical applications.

CIC/ Cable in Conduit

Cable in conduit is a great labor saver if you know the exact length of your cable and conduit runs. Your cable is placed directly into the conduit eliminating the need to pull wire after the conduit has been placed in the ground. Conduit size can be from 3/4in to 6in in a sch40, sch40ul, sdr11 and sdr13.5 thickness. Wire can be from a 16 gauge to a 750 mcm along with medium voltage cable and fiber optic cable installed.  Minimum footage is 500ft. with a maximum of 2500ft.

Advantages:

• Less waste of wire and duct.
• All work is done at one time.
• Lengths made to order.
• Eliminates extra job of cable installation.
• Cable is protected from cuts and nicks by being preinstalled in duct.

Disadvantages:

• Minimum on amount that can be run.
• Must know exact amount needed.

About the Author

Chapman Electric Supply is located in Noblesville, Indiana and is a family owned business. Chapman provides electrician's tools and underground utility supplies.

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