EMT buried in earth

[dhalleron]

I have an insurance company questioning me when I said I can't replace a damaged underground EMT feed to a sign with EMT. I said I would need to replace it with something other than EMT such as PVC.

My experience with EMT is it will completely rust out over time when buried. Sometimes it can't handle just being on a wall outside.

Article 358.10 states EMT can be installed in direct contact with the earth where protected by corrosion protection and approved as suitable for the
condition.

This NEMA document states EMT buried in the earth is generally required to have supplementary corrosion protection.
https://www.nema.org/Technical/Documents/UL%20and%20NEC%20Reg%20for%20Corrosion%20Protection%20of%20Steel%20Conduit%20and%20Electrical%20Metalling%20Tubing.pdf

What say you on EMT buried in the earth and what about "supplemental" corrosion protection?

Thanks,

 

[Dennis Alwon]

IMO, emt will rust out in most environments. I would not install it in the earth especially when we have pvc available

 

[CJW66]

Emt is NOT allowed to be buried in earth!! It is a wet location! You need to run rigid pipe. PVC is the obvious choice and a lot cheaper than rigid steel or aluminum.
First I've EVER heard of emt being buried in the ground..
Just tell them the original installation was WRONG!

 

[iwire]

Emt is NOT allowed to be buried in earth!! It is a wet location!

The NEC allows EMT in wet locations.

It also specifically allows EMT underground under certain conditions.


That said, I agree with Dennis, I would not do it, I would use PVC.

 

[ActionDave]

Emt is NOT allowed to be buried in earth!! It is a wet location! You need to run rigid pipe. PVC is the obvious choice and a lot cheaper than rigid steel or aluminum.
First I've EVER heard of emt being buried in the ground..
Just tell them the original installation was WRONG!

It's allowed, in the US anyway. It is also one of the worst ideas ever.

 

[iwire]

It is also one of the worst ideas ever.

:thumbsup:

 

[CJW66]

It's allowed, in the US anyway. It is also one of the worst ideas ever.

Really?? Why would ya though? Lol. Do you also have to use raintight couplings? Lol

 

[dhalleron]

Yeah I know it is stupid. Insurance company wants a better reason than that.

Anyone know what this "supplemental" corrosion protection for buried EMT is?

 

[iwire]

Yeah I know it is stupid. Insurance company wants a better reason than that.

Anyone know what this "supplemental" corrosion protection for buried EMT is?

I think there is a pipe wrap for this application, Fullthrottle (Randy) has mentioned it.

Tell them PVC costs less.

 

[iwire]

http://www.homedepot.com/p/2-in-x-50-ft-20-Mil-Pipe-Wrap-Tape-53550/100179778

 

[mgookin]

Tell the INSURANCE company that burried EMT has a tendency to corrode rapidly and chafe the insulation on the wires and SHOCK and ELECTROCUTE people and for a reasonable fee, you can use PVC.

 

[peter d]

Who in their right mind would run EMT in the ground? :blink::?

 

[Dennis Alwon]

Who in their right mind would run EMT in the ground? :blink::?

I have seen it around here from many years ago-- maybe before pvc was around, IDK

 

[gadfly56]

Yeah I know it is stupid. Insurance company wants a better reason than that.

Anyone know what this "supplemental" corrosion protection for buried EMT is?

Probably using a sacrificial anode, magnesium alloy most likely. See here. For 1" EMT, likely one per hundred feet is fine, depending on soil conductivity.

 

[MasterTheNEC]

This may be helpful for you...

https://steeltubeinstitute.org/steel-conduit/resources/installation-guides/corrosion-protection/

While many do not like it.....the protection already applied to Galvanized EMT is to protect against a corrosive environment. It is the severely corrosive environments that demand just a little bit more. I agree the best answer would tend to PVC. However, as you will see with the link it is not the only answer and to each his own.