Advice on Installing a Junction Box to Existing Drywall to Reroute ENT
Rerouting Electrical Non-Metallic Tubing (ENT), commonly known as "Smurf Tube" due to its distinct blue color, poses a unique challenge when the drywall is already in place. Unlike standard Romex, ENT is a raceway system, and any modifications must maintain the integrity of the "pull" while adhering to strict electrical codes regarding accessibility.
If you are moving a switch, outlet, or data port and need to splice or redirect ENT, follow this guide to ensure a safe and code-compliant installation.
1. The Golden Rule: Accessibility
The most important rule in the National Electrical Code (NEC) regarding junction boxes is that they must remain accessible. Never bury a junction box behind finished drywall.
- If you are installing a box to reroute ENT, it must have a cover plate that remains visible on the wall surface.
- If you wish to hide the reroute entirely, you must pull new continuous conductors from the original source to the new destination, effectively using the old box location as a pass-through or abandoning it correctly.
2. Choosing the Right "Old-Work" Box
Since the drywall is already up, you cannot use a standard nail-on box. You need an "Old-Work" (or Cut-In) box. However, because you are using ENT, you have specific requirements:
- Plastic vs. Metal: Plastic old-work boxes with "swing-out wings" or "ears" are standard. Ensure the box is deep enough (at least 2-1/8 inches) to accommodate the ENT connectors and the volume of the wire splices.
- ENT Snap-in Connectors: You must use specific ENT-to-box connectors. Do not simply shove the blue tubing into a standard Romex pry-out slot; it will not be secure and will violate code.
3. Step-by-Step Installation Process
Step 1: Locate Studs and Obstructions
Use a stud finder to ensure your new junction box location is between studs. Check for plumbing or gas lines that might be sharing the wall cavity. Since you are rerouting ENT, you need to know which direction the existing tubing is coming from to minimize the "bend radius."
Step 2: Trace and Cut
Most old-work boxes come with a template. Trace the outline on the drywall. Use a drywall saw to cut the hole, being careful not to cut into the existing ENT or wires behind the wall. Pro Tip: Vacuum the dust as you cut to keep the finished room clean.
Step 3: Fish and Secure the ENT
Pull the existing ENT toward the new opening. If the ENT is stapled to a stud deep inside the wall, you may need to carefully cut a small "inspection hole" to release it.
- Attach the ENT connectors to the ends of the tubing.
- Snap the connectors into the knockouts of the old-work box.
- Slide the box into the drywall opening.
Step 4: Tighten the Box
Tighten the screws on the old-work box. This will engage the "wings" behind the drywall, sandwiching the box securely against the wall. Do not over-tighten, or you may crack the gypsum board.
4. Managing Bend Radius
One of the biggest mistakes when rerouting ENT in a finished wall is creates a "kink." ENT is flexible, but it has a minimum bend radius. If you bend it too sharply to fit it into a shallow wall cavity, you will never be able to pull new wires through it in the future. Aim for sweeping curves rather than 90-degree angles.
5. Splicing the Wires
Once the box is installed and the ENT is secured:
- Pull your wires into the box.
- Ensure at least 6 inches of free conductor is available for splicing.
- Use appropriate wire nuts or lever-connectors (like Wago) for the splices.
- Finish with a blank cover plate (or a device if the reroute ends at an outlet/switch).
Conclusion
Installing a junction box to reroute ENT in existing drywall is a practical solution for home remodels, provided you respect the requirement for accessibility. By using the correct old-work hardware and maintaining a smooth bend radius, you ensure that your home's electrical raceway remains functional for future upgrades. Always consult with a local building inspector if you are unsure about specific regional amendments to the NEC.
