Liquid tight conduit is a critical component in protecting electrical wiring systems from moisture, dust, and other environmental hazards. Improper installation can lead to costly downtime, safety risks, and code violations.

This comprehensive guide provides step-by-step instructions on how to properly install liquid tight conduit, including the tools and materials needed, different types of conduit, and troubleshooting tips. By following these best practices, you can ensure a reliable, code-compliant installation that will stand the test of time.

Tools and Materials You’ll Need

Before beginning the process of installing liquid tight conduit, gather the necessary tools and materials:

• Liquid tight conduit (appropriate length for your application)
• Conduit fittings (straight, 90-degree, and other shapes as needed)
• Tape measure
• Conduit cutting tool (specialized cutter or fine-toothed hacksaw)
• Reaming tool or round file
• Adjustable wrench or specialized fitting wrench
• Mounting hardware (conduit clamps, brackets, screws)
• Screwdriver or power drill
• Clean rags
• Degreaser or conduit cleaner

Installation Steps

1. Measure and Cut the Conduit

Using the tape measure, determine the required length of conduit for your run, adding a few extra inches for any necessary bends or terminations. Mark the conduit at the desired length. Using the conduit cutting tool or hacksaw, carefully cut the conduit at the marked location. Ensure the cut is clean and perpendicular to the conduit body.

2. Clean the Conduit

After cutting, use the reaming tool or round file to remove any sharp edges or burrs from the inside and outside of the conduit ends. This will prevent damage to the conductor insulation during wire pulling. If the conduit is dirty or greasy, clean the ends thoroughly with a clean rag and degreaser or specialized conduit cleaner. A clean surface will ensure proper adhesion of the fittings.

3. Install the Fittings

Select the appropriate fittings for your application and slide them onto the prepared conduit ends. Liquid tight fittings have a sealing ring and a compression nut. Ensure the sealing ring is properly seated in its groove and the compression nut threads are aligned with the conduit body. If necessary, apply a thin coat of manufacturer-approved lubricant to the threads to aid in tightening.

4. Tighten the Fittings

Using the adjustable wrench or specialized fitting wrench, tighten the compression nut on each fitting. Follow the manufacturer’s torque specifications to achieve a watertight seal without over-tightening, which could damage the components. As you tighten, the sealing ring will compress, creating a barrier against moisture and debris ingress.

5. Secure the Conduit

With the fittings installed and tightened, position the conduit assembly in its final location. Use conduit clamps, brackets, or other mounting hardware to secure the conduit to structural elements at regular intervals as specified by local electrical codes. Ensure the mounting hardware is tightened adequately to prevent movement or sagging of the conduit. If using screws, use a screwdriver or power drill to drive them securely into place.

Different Types of Liquid Tight Conduit and Installation Requirements

There are two main types of liquid tight conduit: Liquid-tight Flexible Metal Conduit (LFMC) and Liquid-tight Flexible Nonmetallic Conduit (LFNC). Each type has specific characteristics and installation requirements that must be considered.

LFMC

LFMC features a galvanized steel core covered by a PVC jacket. This construction makes it highly resistant to crushing, abrasion, oils, and solvents. LFMC is suitable for dry, damp, or wet locations, and can be used indoors or outdoors.

When installing LFMC:

• Use approved connectors and fittings designed for LFMC
• Support the conduit every 4.5 feet and within 12 inches of terminations
• Maintain the conduit’s minimum bend radius to avoid kinks or damage
• Properly bond the metallic core for grounding continuity
• Seal exposed threads or openings with approved sealants

LFNC

LFNC is made from PVC and does not contain any metal components. It provides resistance against moisture, oil, and corrosive substances. LFNC is lightweight, flexible, and suitable for wet or corrosive environments.

Key installation points for LFNC:

• Use listed connectors and fittings compatible with LFNC
• Support the conduit every 3 feet and within 12 inches of terminations
• Do not exceed the conduit’s maximum pulling tension during wire installation
• Protect LFNC from direct sunlight unless rated for sunlight resistance
• Apply a coating on cut ends to prevent moisture ingress

Both LFMC and LFNC must be securely fastened and supported along their entire length. Comply with the conduit fill allowance and the number of bends permitted between pull points. Ensure that fittings are properly installed and liquidtight to prevent moisture intrusion.

What Wire Do I Run in Liquid Tight Conduit

In general, you should use wire that is rated for wet locations and has a temperature rating suitable for the ambient conditions.

Some common wire types used in liquidtight conduit include:

• THHN/THWN: This PVC-insulated wire is rated for wet or dry locations up to 90°C. It’s a versatile choice for many residential, commercial, and industrial applications.
• XHHW: Cross-linked polyethylene insulation makes this wire moisture and heat-resistant up to 90°C. It’s often used in wet or corrosive environments.
• MTW: Moisture, heat, and oil-resistant, machine tool wire (MTW) is rated up to 105°C for use in wet or oily industrial locations.
• SOOW: This oil-resistant portable cord has a neoprene or TPE jacket designed for hard usage in wet locations up to 90°C. It’s commonly used to connect equipment subject to movement.

Troubleshooting Common Issues

Even with proper installation, issues can arise with liquidtight conduit systems. Here are some common problems and troubleshooting tips:

• Leaks at Connections: Check that fittings are properly tightened and sealing gaskets are in place. Replace any damaged fittings or gaskets. Make sure the conduit is cut square and deburr the inside edge to prevent damage to the gasket.
• Conduit Jams During Wire Pulling: Exceeding the recommended fill percentage can make wire pulling difficult. Check the conduit size and wire fill. Make sure the conduit interior is smooth and free of burrs or debris. Use wire pulling lubricant to reduce friction.
• Loose Fittings: Vibration can cause fittings to loosen over time. Periodically check and tighten all connections. Consider using conduit sealing glands or threadlock for high-vibration environments.
• Damaged Conduit: Inspect conduit runs regularly for signs of wear, kinks, or crushing. Replace any damaged sections to maintain conduit integrity and avoid wiring faults. Use proper support and protection in high-traffic areas prone to physical damage.