UNDERWATER Conduit System for Electrical

FRE Composites’ Underwater Conduit system is a low priced
alternative to expensive aerial and submarine cable.


FRE Composites’ Underwater Conduit system is a low-priced alternative to expensive aerial and submarine cable. FRE® Underwater Conduit system will conform to crossing trench floors and can accommodate irregular trench profiles. Although flexible, the FRE® Underwater duct can take the pressure of depths up to one hundred feet (100ft / 30m).

FRE® Underwater duct crossings don’t detract from the natural beauty of marine areas and protect your cables, and, unlike expensive aerial systems, are not damaged by ice and wind. The secure joint couplings, with the use of Bullnose Pulling Eyes, permit continuous lengths of duct to be pulled at one time, eliminating expensive cofferdams.

At FRE Composites, we have two options available for your underwater conduit system: conduit in casing and standard wall.

Underwater Conduit System: IPS Series

IPS (Iron Pipe Size) is the sizing system that measures the conduit’s outside diameter as the constant value. The FRE® Underwater IPS conduit is manufactured with nominal wall thickness and is designed with a custom casing system.

The casing system helps conduit banks conform to irregular trench floors, river beds and lakes - something that’s particularly beneficial when dredging or trenching are not viable and additional protection is required. FRE® offers custom underwater conduit casing either in factory or at the project site.

Underwater Conduit System: ID Series

Like the IPS Series, the FRE® Underwater ID Series is recommended for submarine trench profiles and natural river and lake beds. The ID sizing system measures the inside diameter as the constant value. The FRE® Underwater ID conduit is constructed with standard wall thickness, which varies based on the conduit diameter (3½, 4, 4½, 5, or 6 inches).

The standard length of FRE® Underwater Conduit is 19.68ft (6m), but if required, it is also available at 39ft (12m). To simplify installation, each length of conduit is supplied with an integral inside-tapered bell on one end and a spigot on the other. The included splice kit ensures a strong and watertight joint system.

Industry Applications

An underwater conduit system is often selected in place of aerial systems because it can be installed year-round. Environmental factors play no part in the installation, meaning there are no unnecessary stoppages. Additionally, no suspension or extensive digging is required, unlike their above-ground counterparts.

The FRE® Underwater Conduit is a translucent epoxy conduit with a specially formulated resin system that offers high mechanical strength and enough flexibility for even complex installations on irregular lake and river beds. Our epoxy fiberglass is a non-toxic and saltwater-resistant cable that does not create harmful chemicals to marine life.

Typically, the FRE® Underwater Conduit is installed through rivers and other water crossings by telecom and power providers. Industry users include Southern Nevada Water Authority (SNWA) and Hydro Quebec - one of the world’s largest hydropower producers.

Advantages of Marine Electrical Conduit

FRE® Underwater Conduit has a range of advantages for underwater projects over other commonly used conduits, and indeed aerial and submarine ducts.

Ease of assembly
The conduit’s light weight makes installation easy, and the push-fit spigot and bell design further facilitate assembly.

Safe & short pull time
The secure joint couplings permit continuous lengths of Underwater FRE® conduit to be pulled at once, eliminating expensive and time-consuming cofferdams.

Environmentally friendly
The conduit does not detract from marine areas’ natural beauty and isn’t damaged by environmental factors.

Unaffected by water, saltwater or most other chemicals.

Flexible and impact-resistant
Flexibility that can conform to irregular lake or river beds.

Low coefficient of friction
Lower coefficient of friction than steel, resulting in labour savings and less stress on cables.

Cable fusion
Fiberglass is an excellent insulator and does not weld with cable.

No burn-through
Strong resistance to being cavitated or pierced as a result of rope pull.

Why Choose FRE Underwater Conduit

FRE Composites’ Underwater Conduit systems are used globally as an economical and long-lasting alternative to PVC, HDPE, RGB, and conduit. We have been designing, developing and producing the best fiberglass products in the business since 1958.

Our team has engineered conduit installations in North America, South America, the Far East, South East Asia, the Middle East and Africa, ensuring the most stringent industry requirements for safety are met.

Get in touch with us today to find the solution to your underwater project.


  • Flexibility and easy installation
  • Lowest installation cost
  • Excellent impact and compressive resistance


  • Complete line of conduit from 2” ID (51 mm) to 6” ID (152 mm)
  • Capacity to design to specific requirements up to 30” (759 mm) casing with innerducting system
    (Best Market Award 2002 - JEC Paris, France)
  • All joints are spliced in continuous length on shore and pulled at once as a complete assembly
  • Can be installed year round


  • Chemical Inertness. Salt water resistance
  • Contains no chlorine, halogen or other toxic materials
  • Low coefficient of friction. Smooth inner wall results in longer cable pulls



Underwater applications


For under water applications