Five Inch (129mm) Electrical Conduit

Five Inch 5″ is the trade size, not the actual dimension of electrical conduit.  One hundred twenty nine 129 is the metric designator not the actual dimension in millimeters.  The dimensions for various types of 5″ electrical conduits are below.  The information was derived from several sources and should not be considered precise.  Dimensions may vary slightly between manufacturers.

Five Inch Electrical Conduit Dimensions

5″ (129) Rigid Metal Conduit (RMC) is a heavy weight conduit with a galvanized finish throughout.  It has factory threads with a 3/4″ per foot taper, 8 threads per inch NPT.  100′ of 5″ RMC weighs approximately 1400 pounds or 634.9 kilograms.  It has an inside diameter of 5.073″ or 128.85mm.  It has an outside diameter of 5.563″ or 141.30mm.  The wall thickness is .245″ or 6.20mm.  5″ Rigid requires a 5 5/8″ hole for the conduit and fittings.  A tap needs a ??” hole.

5″ (129) Rigid Polyvinyl Chloride Conduit (PVC) schedule 40 is a nonmetallic, non-conductive electrical conduit that is good to use indoors and outdoors, or underground.  It has some flexibility with an inside diameter of 5.047″ or 128.1938mm.  It has an outside diameter of 5.563″ or 141.3002mm.  The wall thickness is .258″ or 6.5532mm.  5″ Schedule 40 weighs 315 pounds per 100 feet (142.88148 kilograms).  5″ PVC requires a 5 5/8″ hole for the conduit fittings.  A tap needs a ??” hole.  Threads per inch for the fittings is 8 NPT.

5″ (129) Rigid Polyvinyl Chloride Conduit (PVC) schedule 80 is a nonmetallic, non-conductive electrical conduit that is good to use indoors and outdoors, or underground.  It has limited flexibility.  Schedule 80 has an inside diameter of 4.813″ or 122.2502mm.  It has an outside diameter of 5.563″ or 141.3002mm.  The wall thickness is .375″ or 9.525mm.  5″ Schedule 80 weighs 428 pounds per 100 feet or 194.137376 kilograms.  5″ PVC requires a 5 5/8″ hole for the conduit fittings.  A tap needs a ??” hole.  Threads per inch for the fittings is 8 NPT.

5″ (129) Reinforced Thermosetting Resin Conduit (RTRC or Fiberglass) is a nonmetallic conduit that is suitable for many conditions.  It has an inside diameter of 5.380″ or 136.652mm.  Outside diameter is 5.572″ or 141.5288mm.  The conduit wall thickness is .096″ or 2.4384mm.  100 feet of five inch MW RTRC weighs 120 pounds or 54.43104 kilograms.  It requires a 5 5/8″ hole for the conduit fittings.  A tap needs a ??” hole.  Threads per inch for the fittings is 8 NPT.

5″ (129) High Density Polyethylene (HDPE) is a non-metallic flexible conduit available in long reel lengths to reduce joints and installation time.  It has an outside diameter of 5.563″ or 141.3002mm.  Type SDR-9 has an inside diameter of 4.253″ or 108.0262mm.  100 feet of 5″ HDPE weighs 416 pounds or 188.694272 kilograms.  The wall thickness is .618″ or 15.6972mm.

All five inch 5″ (129) conduit and fittings require a five inch and five eighth 5 5/8″ opening into an electrical box.  The hole can be made with a hole saw or a knockout punch.

A tap for five inch 5″ (129) conduit or conduit fittings requires a ??” hole.  The threads per inch is 8 National Pipe Thread (NPT).

The standard length for most conduits is ten feet 10′ or 3.048 meters.  Twenty foot 20′ (6.096 meters) lengths of metal conduit are available, but not always in stock.  PVC conduit is available in ten foot 10′ and in some sizes, twenty foot 20′ lengths.  RTRC mostly comes in twenty foot 20′ lengths.

See my post describing various electrical conduit types.

Other size electrical conduits:

1/2″ (16)        3/4″ (21)        1″(27)

1 1/4″ (35)        1 1/2″ (41)        2″ (53)

2 1/2″ (63)         3″ (78)        3 1/2″ (91)

4″ (103)         6″ (155)

For more conduit code details and conduit fill see Chapter 9, Tables 1, 4, 5 and 5A.
See the tables in Informative Annex C in the back of the National Electrical Code (NFPA 70) for the allowable number of wires in each size conduit.