Buried EMT

[augie47]

Question submitted from reader by e-mail:
The advisability of doing so not withstanding, is it against Code to install EMT underground and if it is allowed why is it not listed in Table 300.5 ?

 

[ActionDave]

I have never done it, won't do it, don't want anybody else to do it. That said I thought it was ok if you could make it corrosion proof with something like pipe wrap.

 

[jumper]

What about column 3, other approved raceways?

And yes it can be buried. Says so in 358.10(B)

(B) Corrosion Protection.
Ferrous or nonferrous EMT, elbows, couplings, and fittings shall be permitted to be in-
stalled in concrete, in direct contact with the earth, or in
areas subject to severe corrosive influences where protected
by corrosion protection and approved as suitable for the
condition.

Horrible idea though.

 

[GoldDigger]

Horrible idea though.

Even more horrible to try to use it as the EGC!

 

[luckylerado]

What about column 3, other approved raceways?

And yes it can be buried. Says so in 358.10(B)

(B) Corrosion Protection.
Ferrous or nonferrous EMT, elbows, couplings, and fittings shall be permitted to be in-
stalled in concrete, in direct contact with the earth, or in
areas subject to severe corrosive influences where protected
by corrosion protection and approved as suitable for the
condition.

Horrible idea though.

I agree Col 3 but that section could be read to mean special permission is required.

The code goes on to say any fittings must also be listed for wet location.

 

[rlundsrud]

I have seen EMT fitting that stated they were listed for use in concrete if they were wrapped in duct tape. It was a long time ago, and I honestly can't remember the name of the manufacturer, but I kind of laughed when I read it.

 

[donaldelectrician]

I have seen EMT fitting that stated they were listed for use in concrete if they were wrapped in duct tape. It was a long time ago, and I honestly can't remember the name of the manufacturer, but I kind of laughed when I read it.

Why will you wrap EMT in duct tape for a concrete Loco ... people try everything , but no emt in concrete is best .


EMT rots out quick in concrete , really fast if concrete is played with , like in the Florida Keys .


For get using it for a GROUND , my 2 cents worth .



Don

 

[don_resqcapt19]

From the UL White Book for Electrical Metallic Tubing (FJMX).

Galvanized or stainless steel EMT installed in concrete on grade or above generally requires no supplementary corrosion protection. Galvanized steel EMT in concrete slab below grade level may require supplementary corrosion protection.
In general, galvanized steel EMT in contact with soil requires supplementary corrosion protection. Where galvanized steel EMT without supplementary corrosion protection extends directly from concrete encasement to soil burial, severe corrosive effects are likely to occur on the metal in contact with the soil.

 

[Fulthrotl]

I have seen EMT fitting that stated they were listed for use in concrete if they were wrapped in duct tape. It was a long time ago, and I honestly can't remember the name of the manufacturer, but I kind of laughed when I read it.

1984, hotel meridian across from john wayne airport. {Edited to remove the name of the electrical contractor said to be responsible for the installation described below.}

1/2" emt home runs, they'd run 100'+ in a post tension slab,
and then turn down with a red dot 90 above where the panel
would go. they'd turn up wherever, in emt. no GRC where it
would exit the pour. concrete listed fittings. no duct tape.

the concrete paddle machines would grab them during finishing,
and twist them off, leaving the stub looking like the twisted end
of a cigarette that i'm sure the general foreman who thought all
this up was smoking.

3/4" emt home runs, 100' plus, stubbing up into a riser that went
up six floors, feeding that plug in every room. 3/4" emt in the bottom
of the box, 3/4" emt out the top of the box, a 1/2" out the side of the
box to feed a plug down the wall, full house in the bottom, full house
out the top, and a device in the box.... and it's a 104 box.

why no, i'm not a big fan of emt in the slab...... i spent the first two
months working there fixing broken 1/2" emt stubs, and found one
that was tie wired to a post tension cable, that i nicked one day
while dissecting around the emt, not realizing that it was a post tension
cable until it became less tense, all of a sudden.

they make a loud bang, by the way.

 

[tom baker]

EMT is not allowed buried or embedded in concrete in Washington.

 

[iwire]

I agree Col 3 but that section could be read to mean special permission is required.

The code goes on to say any fittings must also be listed for wet location.

Special permission is only required when the section states special permission.

Approved does not require anything in writing.

 

[elf friend]

Wisconsin state code prohibits EMT direct burial also.

 

[rlundsrud]

Why will you wrap EMT in duct tape for a concrete Loco ... people try everything , but no emt in concrete is best .


EMT rots out quick in concrete , really fast if concrete is played with , like in the Florida Keys .


For get using it for a GROUND , my 2 cents worth .



Don

It was just the fittings that had to be wrapped, I was surprised when I saw it, but it was there. I wouldn't do it myself.

 

[don_resqcapt19]

It was just the fittings that had to be wrapped, I was surprised when I saw it, but it was there. I wouldn't do it myself.

EMT is very commonly used in above grade slabs around here, and the tape at the couplings is just to keep the wet concrete out of the pipe. As I recall only set screw couplings are so marked.

 

[kwired]

EMT is very commonly used in above grade slabs around here, and the tape at the couplings is just to keep the wet concrete out of the pipe. As I recall only set screw couplings are so marked.

Exactly, they usually say "concrete tight when taped" meaning exactly what you described - keeps out the wet concrete during the pour.

 

[augie47]

Useful link

Useful link

There are some knowledgeable folks who watch/read our site but don't care to post. Fortunately they add valuable input via messages.
This link on steel conduits is one such example and is, IMO, interesting.
https://steeltubeinstitute.org/steel-conduit/frequently-asked-questions/

 

[jumper]

Anyone who buries EMT or installs it in masonry that is in a wet location should be tarred and feathered IMO.

 

[ADub]

Anyone who buries EMT or installs it in masonry that is in a wet location should be tarred and feathered IMO.

Oops

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[Sparkyva]

I have used imt direct burial before but never emt Imo it would turn to a corroded call back


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[Nutmegger]

If you absolutely must, you can use 3M ScotchWrap or a similar product for corrosion protection of the buried/embedded sections, but the hassle is not worth it IMO.
For buried or embedded, I would transition to rigid and then back to EMT once on the surface.