Galvanized RMC in 1/2–6 in. sizes for bulk electrical supply
We manufacture hot-dip galvanized rigid steel conduit in China for electrical distributors and project buyers. The heavy-wall range includes 5 and 6 in. sizes, alongside smaller threaded lengths, with rigid couplings and elbows available for the same order.
| Product | Galvanized rigid steel conduit (RMC / GRC) |
|---|---|
| Finish | Hot-dip galvanized steel |
| Dimensional series | Steel RMC dimensions under ANSI C80.1 |
| Finished length | Nominal 10 ft, including coupling; approximately 3.05 m |
| Conduit ends | Tapered male NPT threads at both ends |
| Straight connections | Matching rigid conduit couplings |
| Accessory range | Additional couplings and threaded 45° / 90° elbows |
Find the outside diameter, nominal wall and thread pitch for each RMC trade size.
| Trade size (in.) | OD (in.) | OD (mm) | Nominal wall (in.) | Nominal wall (mm) | Threads per inch |
|---|---|---|---|---|---|
| 1/2 | 0.840 | 21.34 | 0.104 | 2.64 | 14 |
| 3/4 | 1.050 | 26.67 | 0.107 | 2.72 | 14 |
| 1 | 1.315 | 33.40 | 0.126 | 3.20 | 11.5 |
| 1-1/4 | 1.660 | 42.16 | 0.133 | 3.38 | 11.5 |
| 1-1/2 | 1.900 | 48.26 | 0.138 | 3.51 | 11.5 |
| 2 | 2.375 | 60.33 | 0.146 | 3.71 | 11.5 |
| 2-1/2 | 2.875 | 73.03 | 0.193 | 4.90 | 8 |
| 3 | 3.500 | 88.90 | 0.205 | 5.21 | 8 |
| 3-1/2 | 4.000 | 101.60 | 0.215 | 5.46 | 8 |
| 4 | 4.500 | 114.30 | 0.225 | 5.72 | 8 |
| 5 | 5.563 | 141.30 | 0.245 | 6.22 | 8 |
| 6 | 6.625 | 168.28 | 0.266 | 6.76 | 8 |
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Nominal dimensions are shown in inches and rounded millimeters. Trade size is the ordering size; OD is the measured outside diameter.
ANSI C80.1 covers rigid steel electrical conduit. Its dimensional series identifies the heavier RMC wall and outside diameter used in this catalog; ANSI C80.6 applies to the separate IMC range.
UL 6 covers steel RMC and related elbows, couplings and nipples. A listing-required purchase needs a verifiable manufacturer, listing record and covered size range. We review those requirements with the material schedule before accepting the order.
RMC is ordered as an electrical raceway. A galvanized water pipe with a familiar thread or trade-size name is not an equivalent purchase: the product identification and electrical-conduit requirements must match the schedule.
The male threads use a 1:16 taper. Thread pitch is 14 TPI for 1/2–3/4 in., 11.5 TPI for 1–2 in., and 8 TPI for 2-1/2–6 in. RMC.
A standard rigid conduit coupling has straight internal threads and joins the tapered male conduit ends. The fitted coupling belongs to the straight-length assembly; extra couplings are separate order items.
Threaded rigid elbows change the direction of the run. Angle and trade size identify the basic item; centerline radius and end dimensions matter where an elbow must fit a fixed layout.
A conduit run can terminate at a threaded hub or through an enclosure opening with the specified entry hardware. Hub, locknut, bushing and sealing requirements belong to that connection, rather than the straight coupling between lengths.
Use threaded fittings marked for RMC or for both RMC and IMC, in the matching trade size. EMT-only couplings and connectors fit a different tube system.
A threadless connector must identify RMC and its trade size. It also needs the end preparation required by its manufacturer; a connector cannot simply grip over the supplied threads unless that installation is expressly permitted.
Heavy-wall steel RMC protects conductors along exposed equipment and service routes. It fits schedules that call for rigid metal conduit where mechanical protection is a priority.
Galvanized RMC can carry outdoor electrical routes to equipment and enclosures. The fittings and enclosure entries must suit the actual exposure; the zinc finish alone does not make a connection watertight.
Steel RMC is used underground, including transitions up to equipment. Corrosive soil or chemical exposure can require supplementary protection, which belongs in the conduit and fitting specification before purchase.
For the lighter threaded option, see our IMC conduit range .
The two largest sizes extend this range beyond our 1/2–4 in. IMC catalog. A stock order can include these larger rigid sizes with their own matching coupling and elbow quantities.
Diameter and wall readings belong with the RMC trade size on the inspection record. A coupling that threads onto the end does not, by itself, prove that the tube has the specified rigid-conduit wall.
Thread inspection looks for torn or flattened crests, debris and correct gauge fit. A coupling that binds at the start needs investigation; forcing it on can damage both mating parts.
Receiving checks include coating damage from straps, supports and unloading. Bare or damaged areas need assessment against the ordered finish before the conduit enters service.
The conductor path needs an unobstructed bore and smooth end edges. Dents, metal chips or sharp burrs can obstruct the pull or damage insulation even when the exterior looks acceptable.
We quote each rigid conduit size by length count, with coupling supply stated on the same line. Elbows and additional fittings appear separately, so a conduit-only price can be compared with a complete material package.
Exposed thread crests need protection from impact during loading and transport. End protectors, supported bundles and lifting clear of the threaded ends reduce damage that can stop a coupling from starting.
Trade size, length count and package identification connect the delivered bundles to the packing list. Large 5 and 6 in. items keep their own counts; an overall tonnage alone cannot verify a mixed-size order.
At a 1 in. trade size, steel RMC has a 0.126 in. nominal wall. The same nominal size in IMC or EMT has a different diameter as well as a thinner wall.
| 1 in. conduit type | OD (in. / mm) | Nominal wall (in. / mm) | Connection |
|---|---|---|---|
| RMC (steel) | 1.315 / 33.40 | 0.126 / 3.20 | Threaded; fittings identified for RMC |
| IMC | 1.290 / 32.77 | 0.093 / 2.35 | Threaded; fittings identified for IMC |
| EMT | 1.163 / 29.54 | 0.057 / 1.45 | Plain ends; EMT couplings and connectors |
Use the conduit type named on the electrical schedule. A shared threaded fitting size can simplify RMC and IMC connections, but changing the conduit still needs the project team’s approval.
Compare plain-end EMT conduitGRC means galvanized rigid conduit. In a galvanized steel electrical-conduit schedule, it names the zinc-coated steel form of RMC. The broader RMC term can also cover other permitted metals or protective finishes, so the material and coating should remain on the purchase order.
Where corrosion protection is required, field-cut threads need an approved electrically conductive, corrosion-resistant compound. Choose a product accepted for that electrical connection and exposure; ordinary decorative paint is not a substitute. Cutting and threading also leave edges and chips that must be removed before assembly.
PVC-coated RMC needs fittings and installation tools suited to its coating system. Coating thickness changes the surface gripped by clamps and bending equipment, and damaged areas need the system’s specified repair treatment. This page covers hot-dip galvanized RMC; PVC coating is a separate product specification.
A mixed-size inquiry can include straight conduit, extra couplings and elbows. We confirm the minimum quantity for each requested size in the quotation. Combining sizes into one shipment does not automatically remove the batch minimum for an individual line.
No. A wet-location marking alone does not establish suitability for a connection that stays underwater. A submerged route needs a fitting and enclosure system identified for that exposure; the conduit’s galvanized finish does not supply that approval.
Use bending equipment and tooling rated for the exact RMC size and required radius. Check the manufacturer's capacity chart before ordering straight lengths for field bending; a machine rated for smaller conduit may not handle 5 or 6 in. RMC. Specify factory-formed elbows where the available equipment cannot produce the required bend.
Send the RMC trade sizes, number of lengths, elbow and coupling quantities, and delivery destination. Include any required manufacturer approval or listing documents so we can price the specified material package.