Is PVC-coated rigid steel conduit permitted to be concrete encased?

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ensley.j

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Hello Forum Members,

I’m seeking clarification regarding the permissibility of concrete encasement for PVC-coated rigid steel conduit under the National Electrical Code (NEC).

  • NEC 352.10(B) permits PVC conduit to be encased in concrete.
  • NEC 344.10(B)(1) allows rigid metal conduit (RMC) to be encased in concrete, provided it is galvanized steel.
However, I have not found a specific reference in the NEC that addresses PVC-coated rigid steel conduit in this context. Is there a section or interpretation that explicitly permits or prohibits its use when encased in concrete?

I appreciate any insights or code references you can share. Thank you in advance for your assistance.
 
The NEC does not have a separate article for PVC-coated rigid steel conduit. It is considered the same as plain rigid steel conduit for that application. You correctly reference 344.10(B)(1) That says:

(B) Corrosive Environments.
(1) Galvanized Steel, Stainless Steel, and Red Brass RMC,
Elbows, Couplings, and Fittings. Galvanized steel, stainless
steel, and red brass RMC elbows, couplings, and fittings shall
be permitted to be installed in concrete, in direct contact with
the earth, or in areas subject to severe corrosive influences
where protected by corrosion protection approved for the
condition.

It is up to the engineer to determine what further protection RMC (and fittings) require when embedded in concrete. I submit none unless the concrete is subject to exposure to corrosives. Consult the respective manufacturers specifications for information.

-Hal
 
Hmm. RMC is permitted to be encased in concrete. PVC is permitted to be encased in concrete. Why would there be any restriction on RMC that is coated in PVC? The NEC doesn't specifically cover this so it would up to the manufacturer of the conduit to determine if it's suitable.
 
The 2026 code added language to address this question.
3440.10(A) Atmospheric Conditions and Occupancies.
(1) Galvanized Steel, PVC-Coated Steel, Stainless Steel, and Red Brass RMC.
Galvanized steel, PVC-coated steel, stainless steel, and red brass RMC shall be permitted under all atmospheric conditions and occupancies.

(B) Corrosive Environments.
(1) Galvanized Steel, PVC-Coated Steel, Stainless Steel, and Red Brass RMC, Elbows, Couplings, and Fittings.
Galvanized steel, PVC-coated steel, stainless steel, and red brass RMC, elbows, couplings, and fittings shall be permitted in concrete, in direct contact with the earth, in direct burial applications, or in areas subject to severe corrosive influences where protected by corrosion protection approved for the condition.
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I'd note the anecdotal reports of water getting through any breaks in the PVC coating and then rusting the _non galvanized_ steel below. You might find plain galvanized conduit is actually more suitable/long term reliable even if PVC coated steel is permitted
 
winnie said:
I'd note the anecdotal reports of water getting through any breaks in the PVC coating and then rusting the _non galvanized_ steel below. You might find plain galvanized conduit is actually more suitable/long term reliable even if PVC coated steel is permitted
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Isn't PVC coated RMC typically manufactured with galvanized RMC? This brand is.
PVC RMC.JPG
 
don_resqcapt19 said:
I have used a couple of brands and it was standard hot dipped RMC with a PVC coating.
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That has been my experience as well. I just figured that it was all manufactured that way. It seems kind of silly to use a bare steel conduit without galvanized protection under the coating.
 
infinity said:
That has been my experience as well. I just figured that it was all manufactured that way. It seems kind of silly to use a bare steel conduit without galvanized protection under the coating.
Click to expand...
Per the UL Guide Information for listed PVC coated rigid metal conduit; "this conduit is also certified under Rigid Ferrous Metal Conduit"
 
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