Electrical Nonmetallic Tubing (ENT)

ENT is the blue corrugated plastic tubing crews nicknamed smurf tube. It bends by hand with no bender, snaps into fittings, and resists moisture and corrosion, which makes it fast to install inside stud walls, above suspended ceilings and encased in concrete.

Its light, flexible wall is also its limitation. ENT generally has to be concealed within walls, floors or ceilings that provide a fire barrier, or otherwise protected, and there are height and exposure restrictions. Being nonmetallic, it always needs a separate grounding conductor pulled inside.

When it applies

ENT, the blue corrugated plastic tubing crews nickname smurf tube, is used concealed — inside walls, in floors, above accessible ceilings. It bends by hand, installs quickly, and resists corrosion, which makes it handy where a metal raceway would be overkill or would rust.

Common mistakes

• Leaving it exposed where it is not permitted, since it needs concealment or protection in many locations.
• Running it in a hot area beyond its temperature limits, where the plastic softens.
• Overfilling it or making rough transitions that make the wire pull miserable.

In the field

ENT saves real time in a masonry wall, but I respect where it is allowed. Concealed and within its temperature rating it performs for decades; used where it can be damaged or overheated, that same convenience turns into a liability.